feat: multisource support in publisher

[jackshen]

Issue: https://github.com/dolbyio-samples/rts-app-react-publisher-viewer/issues/147

Description

In this PR, you can:

• Add new cameras, up to a limit of 4 total (incl. screen shares)
• Add multiple screen shares, up to a limit of 4 total (incl. devices)
• The videos will be displayed in a 1/2/3/4 grid layout
• You can change settings on a per-source basis, incl. name (N.B. name is only saved locally for now)

Code changes

• refactored publisher app to use useMultiMediaDevices hook
• refactored state and logic flowin publisher app to support multisource
• enabled adding multiple cameras
• added basic device selector
• updated video settings onto a per-stream basis
• styled grid view format for multiple videos in publisher

[vishalkharge]

@jackshen

Here are some basic functional issues observed on this PR:

1. There is no way to close the screen share view or additional camera view
2. For screen share view, resolution setting dropdown has undefined value
3. For camera view, microphone and camera toggle buttons are missing
4. For screen view, close/stop toggle buttons are missing
5. Error message 'Failed to execute 'setRemoteDescription' on 'RTCPeerConnection': Failed to set remote answer sdp: Called in wrong state: stable' is shown when publisher goes live.

[jackshen]

@jackshen

Here are some basic functional issues observed on this PR:

1. There is no way to close the screen share view or additional camera view

2. For screen view, close/stop toggle buttons are missing

1 and 4 will be handled in https://github.com/dolbyio-samples/rts-app-react-publisher-viewer/issues/195