ModuleInterface: Print imports with @preconcurrency in swiftinterface files.

When a module has been imported `@preconcurrency` in source, when it is printed
in a `swiftinterface` file it should be printed along with the attribute to
ensure that type checking of the module's public declarations behaves
consistently.

This fix is a little unsatisfying because it adds another a linear scan over
all imports in the source for each printed import. This should be improved, but
it can be done later.

Resolves rdar://136857313.

include/swift/Serialization/SerializedModuleLoader.h

@@ -466,6 +466,9 @@ public:
                 const ModuleDecl *importedModule,
                 llvm::SmallSetVector<Identifier, 4> &spiGroups) const override;
 
+  virtual bool isModuleImportedPreconcurrency(
+      const ModuleDecl *importedModule) const override;
+
   std::optional<CommentInfo> getCommentForDecl(const Decl *D) const override;
 
   bool hasLoadedSwiftDoc() const override;