[mlir][bufferization] Generalize getBufferType

This change generalizes getBufferType. This function can be used to predict the buffer type of any tensor value (not just BlockArguments) without changing any IR. It also subsumes getMemorySpace. This is useful for loop bufferization, where the precise buffer type of an iter_arg cannot be known without examining the loop body.

Differential Revision: https://reviews.llvm.org/D132859