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

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

The problem is that I am not sure yet whether this is a breakage that is intended by this patch, and so SPEC should be fixed, or if that is otherwise something that could be fixed in this patch.

It's bedtime now, my shift for today is over, so I'll only be able to take a look at this tomorrow.

If you can get someone else in the meantime to confirm wether a revert is in order, feel free to do so.

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