Revert "[NFCI][ValueTracking] getUnderlyingObject(): gracefully handle cycles"

This reverts commit aa440ba2.

This has a non-trivial compile-time impact:
https://llvm-compile-time-tracker.com/compare.php?from=0c5b789c7342ee8384507c3242fc256e23248c4d&to=aa440ba24dc25e4c95f6dcf8ff647024f3b12661&stat=instructions

I don't believe this is the correct way to address the issue in
this case.