The planet icon is not very clear for translation feature.
Replace it with the code of the current language.

Task-id: 2028152

Today, some resources that varies very infrequentely are requested on
every page load: the menus, the translations and the qweb templates

After this commit, there will be 2 improvements that will make the
loading of the webclient faster:
1. cache almost static resources forever
when loading the /web/ page, the user session will
contain the cache key to be used to fetch these resources. As the content
of the resource itself it used to compute the hash, the request can be
put in cache by the browser forever (for a year).

The up side is that in general less requests are needed to load the web client
The down side is that the load time and number of queries of /web page
has increased to include what is needed to compute the hash of translations,
menus and qweb templates

2. trigger the loading of the menus before the download (and startup) of
the JS and CSS assets:
The menus contains the definition of the action, wich is the first thing
needed to load a page in odoo. Starting the loading of the menu much
earlier means that when they are not yet in the browser cache (see point 1),
the browser does not need to wait for the entire assets to be downloaded
and parsed before starting the 'load_menu' request, but instead start it
immediately and hold onto a promise to be used instead of the rpc 'load_menu'.

Because the request is done before anything else is loaded, including
JQuery, it is made in vanilla JS.

Co-authored-by: Julien Mougenot <jum@odoo.com>

Part of task 1896658

Co-authored-by: Aaron Bohy <aab@odoo.com>
Co-authored-by: Christophe Matthieu <chm@odoo.com>
Co-authored-by: Mathieu Duckerts-Antoine <dam@odoo.com>
Co-authored-by: David Monjoie <dmo@odoo.com>
Co-authored-by: Martin Geubelle <mge@odoo.com>
Co-authored-by: svs-odoo <svs@odoo.com>
Co-authored-by: Vincent Schippefilt <vsc@odoo.com>

Fix a bunch of ill-documented/incomplete/incorrect method docs
Without this, the automatic doc generation does not work.

Before this commit, the session object was responsible for loading the
translations in the backend only. There was then ugly code in web_editor
(which is also loaded in backend...) which was doing "if frontend then
load translations by myself". This code was also translating templates
while this is the qweb object's job. Now session is always responsible
for loading translation.

Note: the session object should be refactored/split.

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