[mlir][transform] Check for invalidated iterators on payload IR mappings (#66369)

Add extra error checking (in debug mode) to detect cases where an
iterator on "direct" payload IR mappings is invalidated (due to elements
being removed). Such errors are hard to debug: they are often
non-deterministic; sometimes the program crashes, sometimes it produces
wrong results. Even when it crashes, the stack trace often points to
completely unrelated code locations.

Store a timestamp with each "direct" mapping. The timestamp is increased
whenever an operation is performed that invaldiates an iterator on that
mapping. A debug iterator is added that checks the timestamp as payload
IR is enumerated.