[6.2][cxx-interop] Fix unqualified name lookup failure

Explanation: C++ interop synthesizes certain forwarding functions in an
_ObjC module. This confuses MemberImportVisibility. This patch adds
logic to work this around by keeping a mapping between the synthesized
and the original function and looks up where the synthesized functions
belong to based on the original functions' parent module.
Scope: C++ forward interop when MemberImportVisibility is enabled.
Issues: rdar://154887575
Original PRs: #82840
Risk: Low, a narrow change makes getModuleContextForNameLookupForCxxDecl more
precise, and it is only used with MemberImportVisibility.
Testing: Added a compiler test.
Reviewers: @egorzhdan, @tshortli, @hnrklssn

include/swift/AST/ClangModuleLoader.h

@@ -216,6 +216,9 @@ public:
                                           DeclContext *newContext,
                                           ClangInheritanceInfo inheritance) = 0;
 
+  /// Returnes the original method if \param decl is a clone from a base class
+  virtual ValueDecl *getOriginalForClonedMember(const ValueDecl *decl) = 0;
+
   /// Emits diagnostics for any declarations named name
   /// whose direct declaration context is a TU.
   virtual void diagnoseTopLevelValue(const DeclName &name) = 0;