[C++20][Clang] P2468R2 The Equality Operator You Are Looking For

Implement
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2468r2.html.

Primarily we now accept
```
template<typename T> struct CRTPBase {
  bool operator==(const T&) const;
  bool operator!=(const T&) const;
};
struct CRTP : CRTPBase<CRTP> {};
bool cmp_crtp = CRTP() == CRTP();
bool cmp_crtp2 = CRTP() != CRTP();
```

Differential Revision: https://reviews.llvm.org/D134529