[clang] [clang][Interp] Three-way comparisons (PR #65901)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

This has been sitting a while, else I wouldn't feel comfortable reviewing (as I haven't been keeping up on these as much as I should have).  However, I saw 1 issue with the comment I think, else I'm OK with this.  So if you can fix that, I'll approve.

https://github.com/llvm/llvm-project/pull/65901