[clang] Reland "[Utils] add update-verify-tests.py" (#108630)" (PR #108658)

[Erich Keane via cfe-commits]

erichkeane wrote:

>I don't know the solution, but I think there is some inherent flaw when it comes to how -verify tests operate currently, in that you need to trust that the author formatted the test to accurately reflect reality.

In part why I push for bookmarks, it makes it clear on the ordering.  And also why a tool like this makes me afraid, it makes me trust the authors a bunch less.

https://github.com/llvm/llvm-project/pull/108658