[NFC][clang] Fix static analyzer concerns

[Fznamznon]

Summary

IdentifierResolver frees resources in the destructor but doesn't
have user-written copy c'tor or assignment operator, so copying it using
default ones can cause double free.

[aaron.ballman]

LGTM!

[Fznamznon]

Rebase to maybe pass precommit

[Fznamznon]

The failures are unrelated.

clang/include/clang/Sema/IdentifierResolver.h

iterator& operator++() {
         incrementSlowCase();
       return *this;
     }
   };
 
   explicit IdentifierResolver(Preprocessor &PP);
   ~IdentifierResolver();
 
+  IdentifierResolver(const IdentifierResolver &) = delete;
+  IdentifierResolver &operator=(const IdentifierResolver &) = delete;
+
   /// Returns a range of decls with the name 'Name'.
   llvm::iterator_range<iterator> decls(DeclarationName Name);
 
   /// Returns an iterator over decls with the name 'Name'.
   iterator begin(DeclarationName Name);
 
   /// Returns the end iterator.
   iterator end() { return iterator(); }