[clang] [Clang] Fix segmentation fault caused by `VarBypassDetector` stack overflow on deeply nested expressions (PR #124128)

[Boaz Brickner via cfe-commits]

bricknerb wrote:

Please let me know if you have any comments.
I plan to merge this next week (after making the agreed changes) if there are no more comments.

https://github.com/llvm/llvm-project/pull/124128