[Dependency Scanning] Move generation of a named import path 'Identifier' out of the individual scanning workers up into the parent scanner. This operation mutates the scanner ASTContext by potentially adding new identifiers to it and is therefore not thread-safe.

include/swift/AST/ModuleLoader.h

@@ -341,7 +341,7 @@ public:
   /// Retrieve the dependencies for the given, named module, or \c None
   /// if no such module exists.
   virtual llvm::SmallVector<std::pair<ModuleDependencyID, ModuleDependencyInfo>, 1>
-  getModuleDependencies(StringRef moduleName,
+  getModuleDependencies(Identifier moduleName,
                         StringRef moduleOutputPath,
                         llvm::IntrusiveRefCntPtr<llvm::cas::CachingOnDiskFileSystem> CacheFS,
                         const llvm::DenseSet<clang::tooling::dependencies::ModuleID> &alreadySeenClangModules,