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>

Timer test relies on setTimeout(..., 0) for its execution and its
verification. However it seems that in the browser there is *not always*
a guarantee that 2 setTimeout(...,0) will execute in a specific order.

Delaying the verification by 1 ms : setTimeout(..., 1) should force the
order of execution.

closes odoo/odoo#41732

Signed-off-by: VincentSchippefilt <VincentSchippefilt@users.noreply.github.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>

With this commit, most threads show an indicator when a member is typing
something. e.g.

	"Mitchell Stephens is typing..."

Supported threads:

	- DM
	- (public & private) channels
	- Livechat (Website & Backend)

Unsupported threads:

	- mailboxes (e.g. 'Inbox')
	- document thread (= 'Chatter')
	- support channel (with `im_support` module)

Some technical details:

	- This is a mix between 'start'/'stop' and 'regular notify' strategies.
	- On typing text in composer: notify 'start typing' to all members of
	  thread.
	- On clearing text in composer: notify 'stop typing' to all members of
	  thread.
	- A member can only notify once every 2.5 seconds to the server when he
	  starts or stops typing something (throttled, buffered notify call).
	- On receiving a message from someone that is typing: determine that he is
	  no longer typing.
	- On non-empty and unchanged composer text for 5.0 seconds: automatically
	  notifies all members of thread that he is no longer typing anything.
	  (This is like a 'soft / cooperative sender' timeout).
	- On non-receiving a typing notification of someone after 60 seconds:
	  determine that he is not longer typing something (This is like a
	  'hard / receiver assumption' timeout).
	- When some types for more than 50 seconds straight: notify that he is
	  still typing something (again and again every 50 seconds).
	- When two or more people are typing something (Multi-User channels), it
	  displays at most 2 typing users (ordering rule: longer typers first):

	  	"Mitchell Stephens, Marc Brown and more are typing..."

	- Timing summary:

		- Usually 2.5 seconds uncertainty.
    	- Up to 5.0 seconds uncertainty on typer inactivity.
    	- Up to 60 seconds uncertainty on typer page reload / browser tab
    	  closed / etc.

Future Improvements:

	- Detect page reload or browser tab close with loose of longpolling
	  connection

Task-ID 28188