Improve 16x9 Support

Fix stream stop for multiple webcams

Allow audio constraints to be changed in bbb-html5's settings.yml

In some scenarios, there's no need for the browser to apply such audio filters. For example, when user's microphone already does audio filtering (echo cancellation, noise supression ...).
This commit doens't change the current behavior (filters still follow browser's default config): admins need to uncomment/set these values if disabling/enabling specific filters if desired.
This is related to #4873

Video provider's service for local stream control was wrongly setting the disconnected
state when a multiple webcam user tried to stop a single cam. The `stopVideo` method
was inconsistent when called multiple times for the same `cameraId`.

Included a better testing scope for event dispatching and disconnected state handling.

Check if stream already exists before adding in list

Increase camera baseTimeout to 30 seconds (webcam share timeout workaround)

see https://github.com/bigbluebutton/bigbluebutton/issues/11099#issuecomment-753985300

video-preview: improvements to error handling (#9943) and cleanups

It seems the video-preview generic error fallback locale (to handle unexpected errors on our side which do not inherently come from gUM calls) was removed by accident. Adding it back.

Otherwise users who took long enough to accept the gUM permission prompt would fall into the workaround

Some browsers seem to (occasionally) not return the getUserMedia promise call and the
user gets stuck in this state unable to share her/his webcam.

Since enumerateDevices still works even on a gUM rejection this includes a racing
timeout that skips gUM. Configured at settings `gUMTimeout`.

Reproduced with Windows 10 Chrome 87.

The first getUserMedia was not supposed to be considered critical to the whole
video preview flow.

Scenarios where the user has multiple media sources and one of them was already
in use or had some malfunction problem were forcing a global skip at the video
preview modal even if one of them was available to be used.

Collected from https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/getUserMedia

use placeholder in the logger.error method return in the video-preview component. fix wrong file permission.

Add option to generate heap file and tweak metrics

https://github.com/bigbluebutton/bigbluebutton/pull/10826

Fix dangling fi

Provide shorter audio prompts for muted/unmuted

Add keep alive message to audio's websocket 

Prevent calling stopUserTyping when parameters are undefined

Audio client logs already cover audio session progress the way we need.
This avoids keepAlive and other unnecessary messages to be logged in browser's console.
If setting is not present, default value is set to false.

This was added as an option (websocketKeepAliveInterval), which is the interval to send keep alive messages.
Setting websocketKeepAliveInterval to 0 disables the keep alive, producing the same old behavior.
This helps avoid websocket disconnection due to socket inactivity, preventing it to unnecessarily reconnect.
Also, sometimes reconnect fails and error 1005 is triggered.
Fixes problems reported in #10985.
Also reduces occurrences of error 1005.

fix typo in apply-lib.sh

Add processing time metrics