Enable students to share webcam only with moderators

[ffdixon]

Is your feature request related to a problem? Please describe.
In some classes, student want to share webcam but would refer that only the moderator (educator) see their webcam.

Describe the solution you'd like
When students initiate the sharing of webcam, give them the option so to only share this with moderators.

Describe alternatives you've considered
We do have the lock setting for Webcams only visible my moderators, but this applies to all viewers. Here, we want a viewer to have the ability to enable this just for them.