IDETool: Register SourceFile for replaced function body.

This prevents a nullptr dereference in `ASTScope::unqualifiedLookup()` after
querying for the `SourceFile` containing a give source location.

Fixes rdar://137652856 and https://github.com/swiftlang/swift/issues/76944.

lib/IDETool/IDEInspectionInstance.cpp

@@ -354,6 +354,7 @@ bool IDEInspectionInstance::performCachedOperationIfPossible(
           nullptr
         }
     );
+    SM.recordSourceFile(newBufferID, AFD->getParentSourceFile());
 
     AFD->setBodyToBeReparsed(newBodyRange);
     oldSF->clearScope();