[mlir][bufferization] Generalize and rename isMemoryWrite

The name of the method was confusing. It is bufferizesToMemoryWrite, but from the perspective of OpResults.

`bufferizesToMemoryWrite(OpResult)` now supports ops with regions that do not have aliasing OpOperands (such as `scf.if`). These ops no longer need to implement `isMemoryWrite`.

Differential Revision: https://reviews.llvm.org/D141684