[NFC] Replace new getAccessor calls with getOpaqueAccessor calls.

It is fine if we synthesize the accessors a bit more than usual as
PrintAsObjC isn't performance-sensitive and IRGen needs the accessors
anyways.

Author: varungandhi-apple

lib/AST/Decl.cpp

@@ -4930,7 +4930,7 @@ getNameFromObjcAttribute(const ObjCAttr *attr, DeclName preferredName) {
 ObjCSelector
 AbstractStorageDecl::getObjCGetterSelector(Identifier preferredName) const {
   // If the getter has an @objc attribute with a name, use that.
-  if (auto getter = getAccessor(AccessorKind::Get)) {
+  if (auto getter = getOpaqueAccessor(AccessorKind::Get)) {
       if (auto name = getNameFromObjcAttribute(getter->getAttrs().
           getAttribute<ObjCAttr>(), preferredName))
         return *name;
@@ -4960,7 +4960,7 @@ AbstractStorageDecl::getObjCGetterSelector(Identifier preferredName) const {
 ObjCSelector
 AbstractStorageDecl::getObjCSetterSelector(Identifier preferredName) const {
   // If the setter has an @objc attribute with a name, use that.
-  auto setter = getAccessor(AccessorKind::Set);
+  auto setter = getOpaqueAccessor(AccessorKind::Set);
   auto objcAttr = setter ? setter->getAttrs().getAttribute<ObjCAttr>()
                          : nullptr;
   if (auto name = getNameFromObjcAttribute(objcAttr, DeclName(preferredName))) {