async ops, wait for dependencies in threads (#19537)

Makes most operations including memory copies asynchronous except
`enqueueBufferMap`

Worker threads wait for dependent events instead of the main thread.

The state struct is now constructed by the threads instead of being
constructed by the main thread and copied which
1. reduces the capturing overhead in the enqueue lambda
2. enabled removing `mutable` from enqueue lambda

Also removing `#ifdef NATIVECPU_USE_OCK`

Author: uwedolinsky