[mlir][linalg] Add bufferize_to_allocation transform op

This transform materializes a buffer allocation for a given tensor value. All uses of the original value are replaced with the allocation.

Certain non-DPS ops may have an optimized lowering path that bufferizes the entire defining op. Such optimization is added for `tensor.pad` as part of this change.

The resulting IR can be further bufferized with One-Shot Bufferize.

Differential Revision: https://reviews.llvm.org/D144022