[mlir:Async] Remove async operations if it is statically known that the...

[mlir:Async] Remove async operations if it is statically known that the parallel operation has a single compute block

Depends On D104850

Add a test that verifies that canonicalization removes all async overheads if it is statically known that the scf.parallel operation will be computed using a single block.

Reviewed By: herhut

Differential Revision: https://reviews.llvm.org/D104891