[clang] [Clang][Concepts] Fix the constraint equivalence checking involving parameter packs (PR #102131)

[Younan Zhang via cfe-commits]

zyn0217 wrote:

> should we rename SubstituteConstraintExpressionWithoutSatisfaction to make it clear it only works to compare them?

Good idea. How about `SubstituteConstraintExpressionForEquivalenceChecking` then? We can rename it in the next PR.



https://github.com/llvm/llvm-project/pull/102131