Adding some baseline analytics metrics

[pweids]

This is a prototype/example for the baseline metrics project (https://linear.app/rerun/project/implement-baseline-usage-and-behavior-metrics-1e7a95fd0552).

I've implemented a few things here:

• added the number of recordings opened to the open_recording event
• added a switch_recording event, along with method (file_open, ui_click, auto, hotkey eventually)
• added a playback_session event that tracks some playback metrics

The playback_session is not entirely functional, nor do the numbers entirely make sense. But it gets at the right idea.

Here's an example of the new types:
Open Recording

Switch Recording

Playback Session

The numbers don't entirely make sense in Playback Session, especially with frames, so I need to do another round of thinking on this before it can be viable.

Again, this is meant to be a prototype, or just an example, of what implementing these few metrics could look like. Hopefully it's helpful!

[github-actions]

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Result	Commit	Link	Manifest
✅	c17555f	https://rerun.io/viewer/pr/11355	+nightly +main

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