[mlir][func] Remove `func-bufferize` pass (#114152)

The dialect conversion-based bufferization passes have been migrated to
One-Shot Bufferize about two years ago. To clean up the code base, this
commit removes the `func-bufferize` pass, one of the few remaining parts
of the old infrastructure. Most bufferization passes have already been
removed.

Note for LLVM integration: If you depend on this pass, migrate to
One-Shot Bufferize or copy the pass to your codebase.