[mlir][Linalg] Remove alloc/dealloc pair as a callback.

The alloc dealloc pair generation callback is really central to the
bufferization algorithm, it modifies the state in a way that affects
correctness. This is not really a configurable option. Moving it to
BufferizationState removes what was probably the reason it was added
as a callback.

Differential Revision: https://reviews.llvm.org/D114417