[CSSPGO] Unblock optimizations with pseudo probe instrumentation part 2.

[CSSPGO] Unblock optimizations with pseudo probe instrumentation part 2.

As a follow-up to D95982, this patch continues unblocking optimizations that are blocked by pseudu probe instrumention.

The optimizations unblocked are:
		- In-block load propagation.
		- In-block dead store elimination
		- Memory copy optimization that turns stores to consecutive memories into a memset.

These optimizations are local to a block, so they shouldn't affect the profile quality.

Reviewed By: wmi

Differential Revision: https://reviews.llvm.org/D100075