[cxx-interop] Refactor: do not rely on Clang module importer being available

This makes sure that we can emit a pch from a C++ header that uses `CF_OPTIONS`.

rdar://112225263

include/swift/AST/ClangModuleLoader.h

@@ -306,9 +306,6 @@ public:
   virtual EffectiveClangContext getEffectiveClangContext(
       const NominalTypeDecl *nominal) = 0;
 
-  virtual const clang::TypedefType *
-  getTypeDefForCXXCFOptionsDefinition(const clang::Decl *candidateDecl) = 0;
-
   virtual SourceLoc importSourceLocation(clang::SourceLocation loc) = 0;
 };