[mlir][bufferization] Add DeallocOp canonicalizer to remove memrefs also...

[mlir][bufferization] Add DeallocOp canonicalizer to remove memrefs also present in the retained list

Since memrefs in the retained list will never be deallocated, we can remove them from the list of memrefs to be deallocated. If the list of memrefs to deallocate becomes empty, we can just delete the dealloc operation.

Reviewed By: springerm

Differential Revision: https://reviews.llvm.org/D156186