* Plumbing for e2e pings.
* linter fixes
* Re-use existing event instead of introducing a new one.

* Do not send analytics periodically.
* Stop sending e2eping after 5 responses (or 10 requests with no response).
* Pace requests based on conference size.
* Only send e2eping in one direction in a pair of endpoints.

* feat: Adds the user's region to presence. Fixes typos.

* feat: Measures end-to-end RTT with ping over the data channel.