add receiveTime to metadata

[guidou]

We have an open issue for adding capture timestamps and a PR under review to encoded frames.

I'd like to add a receiveTime, in order to have the same set of timestamps as we are proposing for raw frames and defined here

[dontcallmedom-bot]

This issue had an associated resolution in WebRTC December 2024 meeting – 10 December 2024 (Timing info for Encoded Frames):

RESOLUTION: proceed with adding receiveTime to Encoded* Metadata