Android specific thread pool that keeps threads attached to JVM

[LukasPaczos]

Closes #14048.

This PR adds a possibility to listen to thread's lifecycle within the thread pool and changes the Android's shared thread pool implementation to attach each of the threads in the pool to the JVM. This way, we are not constantly attaching/detaching JVM to those threads which was forcing GC runs.

[LukasPaczos]

Comment addressed. Just noting that I still need to make sure that https://circleci.com/gh/mapbox/mapbox-gl-native/264818 was not introduced by this PR.

[LukasPaczos]

I've run CI jobs multiple times and couldn't catch the issue from #14450 (comment), neither could I reproduce locally. I think it's safe to say that it was a one-time occurrence, but I will monitor it further.

Anyway, this is ready for another round.

[tmpsantos]

@LukasPaczos can we hold on this until we land #13935 ?

[LukasPaczos]

Sure, what's the timeline for #13935 @tmpsantos?

[tmpsantos]

Sure, what's the timeline for #13935 @tmpsantos?

2 weeks

[LukasPaczos]

Thanks a lot for all the feedback! Since #13935 landed, I've changed the PR a little bit and it's ready for another round.

[LukasPaczos]

I've re-written to PR to follow @tmpsantos suggestion to use platform::. While the previously proposed TheadLifecycle might be more versatile, there'd be no use in this versatility as of now, therefore a simpler solution is definitely better.

Stale