Polling system

[armanbilge]

Builds on top of

• Integrated timers #3219
• Initial sketch of PollingSystem #3278
• Yet another polling system sketch #3296
• Native Polling System #3314

Downstream integrations:

• Adopt PollingSystem API armanbilge/fs2-io_uring#35
• Use CE polling system for non-blocking I/O on Native fs2#3087
• Implement I/O with CE polling system on JVM fs2#3091

[armanbilge]

Daniel and I discussed on Discord earlier today. Our working plan is to merge this PR into series/3.x more-or-less as-is, very soon. Then we will continue revising as follow-up PRs, particularly the encoding. The hope is that this strategy will make it easier to collaborate :)

[armanbilge]

I published 3.6-e9aeb8c. I'll work on updating my FS2 PR next and then publish a snapshot of that as well. Together that should be sufficient for testing Ember.

[armanbilge]

I published FS2 3.8-1580d81. Anyone should be able to try this today with http4s Ember, Skunk, etc.