A lock-free bounded queue

[polytypic]

This implements a lock-free bounded queue — blocking using domain-local-await.

The data structure / algorithm is based on the Michael-Scott queue extended with length maintenance and caching of remaining capacity in such a way that additional contention is avoided in the happy paths.

TODO:

• [x] fix opam files to build on CI
• [x] use backoff from separate package
  • [x] fix dune-project
• [ ] try_push, length (can be done in O(1)), is_empty
• [ ] tests
• [ ] ability to change capacity
• [ ] benchmarking
• [ ] consider whether making wakeups fair is worth it (currently all awaiters are woken up so there is no fairness)
• [ ] documentation

[polytypic]

FYI, I will squash this PR to a single commit to make this PR a little bit easier to work with.

[polytypic]

FYI, I changed this to use Picos instead of DLA.