Add sender report trace event

[GithubUser8080]

This PR adds a trace event for incoming RTCP sender reports from producers, to provide timestamp information in the node API. Covers use cases of server-side stream synchronization (like recording).

Usage

producer.enableTraceEvent(['sr'])

emits

{
  type: 'sr',
  timestamp: 6348927,
  direction: 'in',
  info: {
    ssrc: 481847794,
    ntpSec: 3911629480,
    ntpFrac: 2788138149,
    rtpTs: 2712133695,
    packetCount: 928,
    octetCount: 75009
  }
}

Resolves issue #1248

[ibc]

Looks good but Rust changes are also required.

[GithubUser8080]

Not familiar with rust so I am relying on the videoroom example for manual testing, hope it is enough.

[ibc]

Just do grep looking for similar FBS types in worker/rust folder and will be easy.

[ibc]

Run cargo fmt to fix lint/clippy formating issues.

[jmillan]

Looks good so far 👍, just a cosmetic naming change requested.

[ibc]

Changelog entry missing and this must be documented in the website (I'll do).

[ibc]

This is not "BWE info".

[ibc]

I'll merge and make this change in v3.

[GithubUser8080]

Thank you