[clang] [clang] Track function template instantiation from definition (PR #112241)

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

Thanks for the report, this is the reduced reproducer:
```C++
template <typename> struct QWindowSystemHelper {
  template <typename EventType> static void handleEvent() {
    QWindowSystemHelper<int>::handleEvent<EventType>();
  }
};
template <>
template <typename EventType>
void QWindowSystemHelper<int>::handleEvent() {
  static_assert(__is_same(EventType, long));
}
template void QWindowSystemHelper<void>::handleEvent<long>();
```

https://github.com/llvm/llvm-project/pull/112241