[memprof] Don't use Frame::hash or hashCallStacks in unit test (#119984)
This patch checks the result of YAML parsing at the level of
MemProfRecord instead of IndexedMemProfRecord, thereby avoiding use of
Frame::hash and hashCallStacks. This makes sense because we
ultimately care about consumers like MemProfiler.cpp obtaining
MemProfRecord correctly; IndexedMemProfData and hash values are just
intermediaries.
Once this patch lands, we call Frame::hash and hashCallStacks only
when adding Frames or call stacks to their respective data structures.
In other words, the hash functions are pretty much business internal
to IndexedMemProfRecord.