Live Stream API - February 21st, 2023 [Feature]

## Feature Added [content encryption](https://cloud.google.com/livestream/docs/how-to/encrypt-content) support ## Feature Added new channel events: [mute](https://cloud.google.com/livestream/docs/how-to/create-channel-events#mute-event), [unmute](https://cloud.google.com/livestream/docs/how-to/create-channel-events#unmute-event), [return to program](https://cloud.google.com/livestream/docs/how-to/create-channel-events#return-to-program-event), and [switch input](https://cloud.google.com/livestream/docs/how-to/create-channel-events#switch-input-event) ## Feature Added [audio loudness normalization](https://cloud.google.com/livestream/docs/reference/rest/v1/projects.locations.inputs#audio) and [audio gain control](https://cloud.google.com/livestream/docs/reference/rest/v1/projects.locations.channels#AudioMapping.FIELDS.gain%5Fdb) ## Feature Added the [timecode feature](https://cloud.google.com/livestream/docs/how-to/use-timecode) which supports synchronizing media workflows with live stream content