Add an option to set a default logo to be placed for all created meetings.

The default logo is inserted as a create meeting param for all meetings that
do not have a `logo` param defined. Two new properties were included at
bigbluebutton-web configuration:

- [Boolean] `useDefaultLogo`: enables/disables the use of the default logo
  disabled as default

- [String] `defaultLogoURL`: The default logo URL to be fetched by the client
  bigbluebutton logo as default

ExternalProcessExecutor spawned sub-processes with stderr and
stdout buffers, but did not read from those buffers. Sub-processes
producing output sometimes would fill up these buffers and then hang
until the timeout occurs and the process is killed.

This fixes #12839 (PDF conversion hangs for 10 seconds per page)
by properly discarding command output. The patch also deprecates an
outdated and dangerous API and offers a safer alternative. Splitting
command arguments based on whitespace may result in unwanted behavior
if an argument (e.g. a filename) contains whitespace.

Quick fix to prevent the moderator who joins the
breakout room from being unable to unmute himself

Implements forceRasterizeSlides (force convert presentation to png before svg) and pngWidthRasterizedSlides (force png width (px))

Send pubSub FileTooLarge Error Msg from bbb-web when file is too large, (and makes Akka send meetingId with presentation token msg)

This PR reduces the impact of #8618 by increasing hardcoded timeout from 7s to 60s

A subsequent PR is going to be sent by @gustavotrott to:

-> Make this timeout configurable;
-> Add a log telling that timeout happened

Follow up to #11681

Moderators are able to send a message to the meeting's guest lobby. This new
event reaches bbb-web and is sent to the guest user with her/his status response
while polling. All guest users that are waiting for acceptance will be able to
read this message.

enableGuestLobbyMessage is disabled by default.

Pad exporter uses this same location to serve pad's downloaded content
but the the match was failing because padId is not the last element
of the URL on that scenario.

Pattern follows /pad/p/<padID>[/export/(format)]?<query>.

Associate pads with meetings so session validation is restricted to the
meeting's valid session tokens.

Meteor will dispatch new redis events on shared notes and closed captions
pads creation. This event will go through apps and reach web to populate
a new meeting's pad collection that contains all valid pad id's for that
session. Nginx will use this collection to check if the user's session token
belongs to the pad's authorized users.

Besides these modifications, an extra change will be needed at notes.nginx.
Location /pad/p/ needs to change it's auth_request:

from /bigbluebutton/connection/checkAuthorization;
to /bigbluebutton/connection/validatePad;

While cherry-picking some of this work I noticed those extras.

Cherry-picked https://github.com/bigbluebutton/bigbluebutton/pull/9855



Co-Authored-By: Pedro Beschorner Marin <pedrobmarin@gmail.com>

Cherry-picked the commits from https://github.com/bigbluebutton/bigbluebutton/pull/9251
The added code checks if a meetingID is unique and makes sure no two meetings use the same VoiceBridge. Also see Issue # 9024