[Macros] Requestify MacroExpansionExpr expansion

The request returns the expanded buffer ID even if it failed to
typecheck the expanded buffer.
This makes refactoring 'Expand Macro' work regardless of the
typechecking results.

rdar://108530760

lib/Refactoring/Refactoring.cpp

@@ -8622,11 +8622,9 @@ bool RefactoringActionAddAsyncWrapper::performChange() {
 /// expression.
 static Optional<unsigned> getMacroExpansionBuffer(
     SourceManager &sourceMgr, MacroExpansionExpr *expansion) {
-  if (auto rewritten = expansion->getRewritten()) {
-    return sourceMgr.findBufferContainingLoc(rewritten->getStartLoc());
-  }
-
-  return None;
+  return evaluateOrDefault(
+      expansion->getDeclContext()->getASTContext().evaluator,
+      ExpandMacroExpansionExprRequest{expansion}, {});
 }
 
 /// Retrieve the macro expansion buffer for the given macro expansion