[MLIR][OpenMP] Changes to function-filtering pass (#71850)

Currently, when deleting the device functions in the second stage of filtering during MLIR to LLVM translation we can end up with invalid calls to these functions. This is because of the removal of the EarlyOutliningPass which would have otherwise gotten rid of any such calls.

This patch aims to alter the function filtering pass in the following way:
	- Any host function is completely removed.
	- Call to the host function are also removed and their uses replaced with Undef values.
	- Any host function with target region code is marked to be removed during the the second stage.
	- Calls to such functions are still removed and their uses replaced with Undef values.

Co-authored-by: Sergio Afonso <sergio.afonsofumero@amd.com>