Bug 2005554 - Kotlin: Rewrite Dispatcher to offload metrics to not cause main blocks

[badboy]

This has a new problem now though:
Not all metrics go through that and could be recorded in a different order.

Is that fine?
I think that's fine because:

1. Same metric types are recorded on the dispatcher, so e.g. counting is always in correct order.
2. Recording of a not-dispatched metric is always unrelated to any other metric, so the precise order doesn't matter either
3. Ping methods are dispatched, so a call to a non-dispatched metric, followed by a dispatched ping submit keeps the correct order.

Note: things still go through the Glean Rust dispatcher, so things are ordered there in the way they come in.