CTAD is not valid with a dependent nested-name-specifier

The following program demonstrates the issue:
```cpp
templatestruct foo{
T x;
};
struct bar{
templateusing baz=foo;
};
templatevoid qux(){
typename T::baz v{0};
}
int main(){
qux();
}
```
CTAD is not valid when the nested-name-specifier is dependent, so this should be rejected. See also: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124687

Start with the provided C++ reproducer and investigate the compiler's class template argument deduction handling for a dependent nested-name-specifier. Locate the relevant semantic-analysis tests and add a regression test showing that this program is rejected, then run the focused compiler test suite to verify the diagnostic and avoid regressions.

Written by the indexing model from the issue text.