[clang] [clang] check deduction consistency when partial ordering function templates (PR #100692)

[Alexander Kornienko via cfe-commits]

alexfh wrote:

@mizvekov another distinct compilation error after this commit (and not fixed by https://github.com/llvm/llvm-project/pull/107972 and other follow-up commits): https://gcc.godbolt.org/z/zMG5nsda3 (reduced from https://github.com/hlslibs/ac_math/blob/20bbf040834c5815b01a9ed8e523e4b0dabecf23/tests/rtest_ac_matrixmul.cpp)

We have a few more cases that still generate this compilation error (`call to X is ambiguous`). I'm trying to reduce those as well.

https://github.com/llvm/llvm-project/pull/100692