Improve the way we observe changes on Users's collection

It is safer to look at subscriptions's state to users instead of depending
on the initial state of the collection at mounting time. Although
i couldn't force any race conditions on this, there's a chance it could
happen. The fix avoid this problem.
This complements #11533

Changes on end meeting message

Fixes incorrectly displaying of 'restore presentation' button when presentation is disabled

Added text for override of bbb-web.properties

add overlay config for bbb-web

there was a call of grep which failed when the config file does not
exist yet. check existance of file first.

Move some validations to the User's collection query

Bbb core http endpoint wip

Also removed unnecessary fields

Improve performance when doing user join notifications

Co-authored-by: Anton Georgiev <antobinary@users.noreply.github.com>

Complements #11533

Replaces the PR #10604, which has been temporarily fixed a problem in 2.3a2, that is, the slide size gets crazy when turning on and off fullscreen mode. Since #10604 was just a workaround, I tried to fix it in a way making more sense.

### Closes Issue(s)

closes #10459 (already closed by #10604) and #10589

### Motivation

#10604 is fixing the problem by calling "slide change" event, although the slide has not been changed actually. I tried to fix the same problem by adding a "full screen change" event listener in the layout manager, which I think is more elegant.

Merge 2.2 into develop

Waiting users audio and push alerts

Fix openPanel errors related to polling and shared notes

Backport audio improvements from 2.3

Revert "Add reconnection and sync handler"

Revert "Fix clear chat for single message"

Without 'exact' match, the browser fallbacks to the default inputDeviceId

This prevents the error (input device error)  when breakout is ended and we try
to skipCheck the microphone when user returns to main room (assuming the
user had the microphone active before joining breakout room).

Prevent toggleMute api call to be called for listenonly
This has no effect to the end user, but avoids unnecessary server calls

Fixes #11490

Fixes #11489

Merge 2.2.[32..35] into 'develop'

Fix audio and push alerts for user join