[clang] [Sema] Avoid deep recursion in AnalyzeImplicitConversions (PR #145734)

[Ilya Biryukov via cfe-commits]

ilya-biryukov wrote:

> My first thought is that this has tried to use more stack than its allowed.

that's probably the case, the test is a complete overkill, I just wanted to make sure we do hit the issue with upstream Clang when adding it.
The buildbot in question is using asan for sure (based on the name), I'll try to reproduce this locally tweaking options and stack sizes to get a reduced version that makes the bot green, but still fails under normal circumstances.

https://github.com/llvm/llvm-project/pull/145734