The wysiwyg abstraction layer was introduced in saas-12.2 by
commit f2969923. Its goal was to provide an external interface
for other modules that wanted to use the editor feature such
that the editor core itself could be changed without requiring
extensive changes in the other modules.

This commit is adapting the wysiwyg interface to instantiate
the 12.0 editor below it rather than the saas-12.2 one, thus
reverting the "new editor" part of f2969923 itself.

Part of PR 35677.

Co-authored-by: Nicolas Bayet <nby@odoo.com>
Co-authored-by: Antoine Guenet <age@odoo.com>
Co-authored-by: Christophe Matthieu <chm@odoo.com>
Co-authored-by: David Monjoie <dmo@odoo.com>

* Creating a new structure by transforming all the plugins in the
  library using the odoo inheritance system. Plugins are easier to
  implement with the AbstractPlugin to add Odoo behaviors.

* From now on, the methods of the library (in this case Summernote) can
  no longer be called by other modules or files. Only the wysiwyg
  widgets can access it, to simplify the updating process. The wysiwyg
  object serves as an interface.

* Depending on the options the snippets will be loaded or not, the
  editor will be in an iframe or not... all of this is transparent from
  the outside.

* Regarding iframes, all controllers related to editing have been
  removed: the new API no longer needs them. This speeds up loading,
  eases testing and removes complexity for the same
  features.

PUBLIC FEATURES

There are several public methods on the Wysiwyg class:
* Wysiwyg.prepare (WidgetParent): returns a deferred resolved when the
  library (xml, lazy, assets...) is loaded.
* Wysiwyg.getRange (DOM): returns the range (selection in the dom)
* Wysiwyg.setRange (startNode, startOffset, endNode, endOffset): creates
  a range (selection in the dom)
* Wysiwyg.setRangeFromNode (DOM, options) that creates a range from an
  element (option available to select all, start or end)

A jQuery selector was added: :o_editable, which indicates whether the
current element is editable. That is, if it is contained in a tag with
the attribute 'contentEditable = "true"' or in a tag with the class
o_editable.
Several methods are also present:
* focusIn: makes a focus and places the cursor at the beginning of the
  element
* focusInEnd: makes a focus and places the cursor at the end of the
  element
* selectContent: makes a focus and selects the content

HTML FIELD

The HTML field can receive different options:
* style-inline: {boolean} transforms a class into an inline style when
  saving and vice versa when reading.
* no-attachment: {boolean} prevents the use of attachments (in media
  dialog)
* cssEdit: {xml_id} to use a template containing the css to loaded in
  an iframe when editing
* cssReadonly: {xml_id} to use a template containing the css to load
  into an iframe when viewing in readonly
* snippets: {xml_id} snippets template (can be used with or without
  cssEdit)
* wrapper: {template} qweb static template (containing a tag:
  id = "wrapper") that will include the content during editing (removed
  on save)

MASS MAILING

A widget was created for mass mailing. There are now two fields:
body_html and body_arch.
body_arch contains the code with the class without conversion into
inline style, useful when editing and one with the inline style that is
visible in readonly mode and sent by email.
Advantage: no spreading errors, able to update css/theme, able to do
more changes when converting to inline style so that a maximum of mail
clients have an impeccable rendering.

Co-authored-by: Antoine Guenet <age@odoo.com>

BS4 "btn-default" class was replaced with "btn-secondary", which makes
more sense.

Odoo made the bad choice of using the 'btn-sm' class for every button
instead of configuring the padding for default 'btn' to be smaller.
In BS4, the style of btn-sm is actually more complex, lowering the
font-size too. Also, btn-xs was removed so we would not have the
possibility to display smaller button than our default ones.

This commit removes btn-sm wherever it was used. Unfortunately, this
might remove it at some places where it made sense but this can be
restored in a second time.

Today, Odoo is really tricky to use without seeing the screen, it must be improved to be usable.

This PR forbid to use labels without a "for" attribute, add some title, rule and aria attributes in HTML. With that, Odoo will be fully usable with a screen reader.


* [IMP] Labels must have a for attribute. Improve accessibility.
* [IMP] Better error message when trying to read a missing cached value
* [FIX] Add some aria-label and title attributes for screen readers.
* [FIX] Template name is not included in the error message in case of SyntaxError in QWeb
* [FIX] Improve the Tour failed at step error message to be more explicit.
* [IMP] Add aria-labels
* [FIX] Add missing aria-label on failing test
* [IMP] aria-hidden means hidden. Fix all bad aria-hidden and hide aria-hidden for all.
* [IMP] Color names on kanban views and many2many tags
* [IMP] Add some checks on views for accessibility.
* [IMP] Add `alt` attribute on `img` tags.
* [IMP] Add aria-label and title on non-described icons
* [IMP] Add button role to widgets with btn class
* [IMP] Translate aria and formatted attributes.
* [IMP] Remove wrong aria-labelledby
* [IMP] Add menu role on dropdowns
* [IMP] Buttons must be focusable
* [IMP] Add aria attributes on progress bars
* [IMP] Improve accessibility of basic widgets
* [IMP] Change main layout to more semantic tags
* [IMP] Add menuitem role when missing
* [IMP] Remove wrong role='presentation'
* [IMP] Improve accessibility of tab panels
* [IMP] Add aria-invalid on invalid fields
* [IMP] Add aria-sort on ordered columns
* [IMP] Add role on alerts
* [IMP] Use dialog role, header, main and footer tags for modals
* [IMP] Add labels on o_status
* [IMP] Improve accessibility of kanban view with feeds and articles
* [IMP] Add alerts in case of new messages
* [IMP] Add widget, navigation or img role to aria-labelled items

The translate feature of widgets html and html_frame had been
broken by the new views refactoring. This commit restores it for
the html widget, and removes it completely for html_frame as it
wasn't working correctly before the new views anyway (moreover,
it had already been disabled for mass_mailing: de403dc1ab440b9b08ea7fce189cd157745dfe74).

This commit also ensures that the changes are correctly saved for
the html_frame widget. Note that this widget still needs to be
converted to our new coding guidelines.

The field widget html wasn't implemented yet in the new views. A
very basic implementation was done in addon web. It only handled
the readonly mode so that the field were displayed in studio.

This commit removes this basic implementation from web, and re-
introduced the old one, converted, in addon web_editor.

This commit introduce a full redesign of all JS views.  We started
basically from scratch.  The goal was to unify all the various views
under a common framework, to make them testable, to make then usable in
different conditions (in studio, or in the frontend), and to make our
lives easier.

Some important points are:
- we introduced new coding guidelines (camelCase, 80 chars width, ...)
- we have a brand new testing framework (still QUnit based)
- kanban view moved to the web addon
- calendar view (formerly web_calender) moved to web as well
- the tree view was removed
- all new code should be documented

We hope that this code is the start of a new era for the Odoo web
client, we want to have a high quality codebase, well documented, well
tested, well designed.

Work done by the framework team: mostly aab, ged, chm, dmo, qsm