[Clang][NFC] Minor constraint satisfaction checking cleanup (#134059)

We had a weird, incorrect, "ConstraintEvaluator" object that was not
useful for anything, so I removed that.

I also changed the CheckConstraintSatisfaction overload that just took
an Expr* as this did not make much sense at all.

Satisfaction checking is still fairly wrong,
we do not follow the standard that requires we only substitute into the
mapping of the normal form, so we produce errors for incorrect
substitution into concepts id, even though we should not.

Author: cor3ntin

clang/include/clang/Sema/Sema.h

@@ -14597,8 +14597,9 @@ class Sema final : public SemaBase {
   /// occurred and satisfaction could not be determined.
   ///
   /// \returns true if an error occurred, false otherwise.
-  bool CheckConstraintSatisfaction(const Expr *ConstraintExpr,
-                                   ConstraintSatisfaction &Satisfaction);
+  bool
+  CheckConstraintSatisfaction(const ConceptSpecializationExpr *ConstraintExpr,
+                              ConstraintSatisfaction &Satisfaction);
 
   /// Check whether the given function decl's trailing requires clause is
   /// satisfied, if any. Returns false and updates Satisfaction with the