perf(providers): replace wake_by_ref with loop

[mattsse]

Motivation

instead of waking up the task when we do a state transition, we poll the next state directly.

Solution

Replace cx.waker().wake_by_ref(); with a loop. This way, the next state is polled immediately and we don't have to rely on the task being polled again right away.

PR Checklist

• Added Tests
• Added Documentation
• Updated the changelog

[gakonst]

i thought that removing the loops was the right way to do it, and defer to the runtime to drive each loop step?

[mattsse]

that's is just additional overhead, because then you delegate state transitions to the executor, which has to wake up the task and call poll again (but now in the next state), when the next state is already ready to be polled (for the first time).

loop does the same thing but immediately
A ready -> B
continue
poll B