[ExtractAPI] reorder the module names in extension symbol graph file names (llvm#119925)

Resolves rdar://140298287

ExtractAPI's support for printing Objective-C category extensions from
other modules emits symbol graphs with an
`[email protected]`. However, this is backwards
from existing symbol graph practices, causing issues when these symbol
graphs are consumed alongside symbol graphs generated with other tools
like Swift. This PR flips the naming scheme to be in line with existing
symbol graph tooling.

Author: QuietMisdreavus

clang/lib/ExtractAPI/Serialization/SymbolGraphSerializer.cpp

@@ -1068,9 +1068,8 @@ void SymbolGraphSerializer::serializeWithExtensionGraphs(
 
   for (auto &ExtensionSGF : Serializer.ExtendedModules) {
     if (auto ExtensionOS =
-            CreateOutputStream(ExtensionSGF.getKey() + "@" + API.ProductName))
-      Serializer.serializeGraphToStream(*ExtensionOS, Options,
-                                        ExtensionSGF.getKey(),
+            CreateOutputStream(API.ProductName + "@" + ExtensionSGF.getKey()))
+      Serializer.serializeGraphToStream(*ExtensionOS, Options, API.ProductName,
                                         std::move(ExtensionSGF.getValue()));
   }
 }

clang/test/ExtractAPI/objc_external_category.m

@@ -46,7 +46,7 @@ @interface ExtInterface
 // Symbol graph from the build without extension SGFs should be identical to main symbol graph with extension SGFs
 // RUN: diff %t/symbols/Module.symbols.json %t/ModuleNoExt.symbols.json
 
-// RUN: FileCheck %s --input-file %t/symbols/ExternalModule@Module.symbols.json --check-prefix EXT
+// RUN: FileCheck %s --input-file %t/symbols/Module@ExternalModule.symbols.json --check-prefix EXT
 // EXT-DAG: "!testRelLabel": "memberOf $ c:objc(cs)ExtInterface(py)Property $ c:objc(cs)ExtInterface"
 // EXT-DAG: "!testRelLabel": "memberOf $ c:objc(cs)ExtInterface(im)InstanceMethod $ c:objc(cs)ExtInterface"
 // EXT-DAG: "!testRelLabel": "memberOf $ c:objc(cs)ExtInterface(cm)ClassMethod $ c:objc(cs)ExtInterface"
@@ -55,3 +55,10 @@ @interface ExtInterface
 // EXT-DAG: "!testLabel": "c:objc(cs)ExtInterface(cm)ClassMethod"
 // EXT-NOT: "!testLabel": "c:objc(cs)ExtInterface"
 // EXT-NOT: "!testLabel": "c:objc(cs)ModInterface"
+
+// Ensure that the 'module' metadata for the extension symbol graph should still reference the
+// declaring module
+
+// RUN: FileCheck %s --input-file %t/symbols/[email protected] --check-prefix META
+// META:       "module": {
+// META-NEXT:    "name": "Module",