[clang] [clang-tools-extra] [clang] Implement CWG2398 provisional TTP matching to class templates (PR #94981)

[Alexander Kornienko via cfe-commits]

alexfh wrote:

Here's a reduced test case: https://gcc.godbolt.org/z/jxer3W39W

As usual, it's hard to say if the code got invalid during automatic reduction, but it at least compiles well with clang before this commit.

https://github.com/llvm/llvm-project/pull/94981