[Clang][Sema] Do not mark template parameters in the exception specification...

[Clang][Sema] Do not mark template parameters in the exception specification as used during partial ordering (#91534)

We do not deduce template arguments from the exception specification
when determining the primary template of a function template
specialization or when taking the address of a function template.
Therefore, this patch changes `isAtLeastAsSpecializedAs` such that we do
not mark template parameters in the exception specification as 'used'
during partial ordering (per [temp.deduct.partial]
p12) to prevent the following from being ambiguous:

```
template<typename T, typename U>
void f(U) noexcept(noexcept(T())); // #1

template<typename T>
void f(T*) noexcept; // #2

template<>
void f<int>(int*) noexcept; // currently ambiguous, selects #2 with this patch applied 
```

Although there is no corresponding wording in the standard (see core issue filed here
https://github.com/cplusplus/CWG/issues/537), this seems
to be the intended behavior given the definition of _deduction
substitution loci_ in [temp.deduct.general] p7 (and EDG does the same thing).