[MLIR] Correct memrefdataflow behavior in the presence of cast and other operations

MemRefDataFlow performs mem2reg style operations for affine load/stores. Unfortunately, it is not presently correct in the presence of external operations such as memref.cast, or function calls. This diff extends the functionality of the pass to remain correct in the presence of such ops.

Differential Revision: https://reviews.llvm.org/D104053