*mail,point_of_sale,web_editor,website

In the tests, required services are deployed for each test
independently. There is no need to have, in additon, all services
deployed globally. Worse, it could conflict and lead to unexpected
results.

This commit ensures services are no longer deployed globally in
tests. It turns the module 'web.env' into a declarative module with
no side-effect, by moving the service deployment to main.js, which
isn't added to the tests page.

Task 2287397

closes odoo/odoo#53817

Signed-off-by: Lucas Perais (lpe) <lpe@odoo.com>

This commit is a significant rewriting of client-side discuss, chatter,
chat window, and messaging menu using OWL. The behavior should be broadly
the same, with some slight functional changes here and there.

From a technical standpoint, the code of messaging is mainly organized in 2
main groups of modules:

- models, which are logical entities that depict the client-side state of
  messaging as a whole.
- components, which are in charge of displaying information from models.

This refactoring also introduces new JS guidelines regarding folder structure
(/static) and naming rules for JS modules.

Community PR: https://github.com/odoo/odoo/pull/39023
Enterprise PR: https://github.com/odoo/enterprise/pull/6249

Task-1914207

This PR is a collaborative work by Alexandre, Julien, Sébastien and Xavier,
with the precious help of Lucas to speed it up towards the end.

closes odoo/odoo#39023

Related: odoo/enterprise#6249
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>
Co-authored-by: Alexandre Kühn <aku@odoo.com>
Co-authored-by: Julien Giannone <jgi@odoo.com>
Co-authored-by: Lucas Perais <lpe@odoo.com>
Co-authored-by: Sébastien Theys <seb@odoo.com>
Co-authored-by: Xavier Dubuc <xdu@odoo.com>

*bus,mail

This commit extracts the common basis of the env to use both in
the frontend and the backend. The public env now contains most of
the features that were previously (only) in the webclient env.

Moreover, the PublicRoot no longer uses the ServiceProviderMixin,
such that services are only deployed once, in the (public) env.

Owl components can now be defined in the website, and rely on a
properly built env. Legacy widgets still works as they access
services through the PublicRoot (via trigger_up) which redirects
those requests to the env.