PURPOSE

Fix frontend rating and clean a bit module organization

SPECIFICATIONS

In order to ease understanding of portal chatter dependencies let us name
files according to guidelines. In this commit we rename a bit files in
website mail to understand which widgets and portal parts are impacted by
website mail bridge module.

Assets are also moved in their own file to ease module discovering.

LINKS

Task 2057301
PR #35870

This split responsiblilies :
- portal provides basic chatter for portal document, and
website documents (slides, blog, ...).
- website_mail provides comments moderation (unpublished mail
message)
- website_rating integrate rating when posting comments

Extend new dynamic chatter to manage rating
when posting comment.

The model should inherit of rating.mixin and
its frontend chatter should allow rating to enjoy
star widget and rating card.

This is more generic : stats, rating, ... are manage
in one place (this module) for all document.

Message are now fetched and display using javascript
to optimize performance.
Also the chatter is completely rewrite : add pager,
filter possiblity, ...

This commit is mainly technical: posting feature does
not change. Only the display with pager is new.
The goal is also to prepare frontend chatter for a
better integration with rating widget.

The mail.thread mixin is extended to manage the field
website_message_ids (display all messages that can be
seen on frontend by user (employee or not).

When fetching or posting message, a check is done to see
if we need to do it as sudo(). website_mail implement posting
messages with token or sha_in (using in website_quote).
The same verification is now done when fetching messages, via
'_special_access_object' method.