[mlir][bufferize] Simplify ModuleBufferization driver

* Bufferize FuncOp bodies and boundaries in the same loop. This is in preparation of moving FuncOp bufferization into an external model implementation.
* As a side effect, stop bufferization earlier if there was an error. (Do not continue bufferization, fewer error messages.)
* Run equivalence analysis of CallOps before the main analysis. This is needed so that equialvence info is propagated properly.

Differential Revision: https://reviews.llvm.org/D123208