Add sync primitives to AsyncRuntime trait

[drmingdrmer]

Yes. Tokio primitives do work in other runtimes, but they are not optimally-supported.

For example, Tokio has its own counters for cooperative multitasking (which, obviously, only make sense and are active if running within Tokio), other runtimes have their own algorithm for how not to block the runtime for too long. The same is true for resource monitoring support (e.g., via tracing in Tokio).

Another issue is that Tokio sync primitives allocate memory at unexpected points. This is OK if you are fine with your program going broken on OOM, but we don't have this luxury :-). We need to handle OOMs properly.

Originally posted by @schreter in #1010 (review)

TODO:

• Add AsyncRuntime::oneshot #1023
• AsyncRuntime::watch
• AsyncRuntime::mpsc
• AsyncRuntime::unbounded_mpsc
• AsyncRuntime::rwlock

[github-actions]

👋 Thanks for opening this issue!

Get help or engage by:

• /help : to print help messages.
• /assignme : to assign this issue to you.