[NFC] Thread DeclNameRef through most of the compiler

This huge commit contains as many of the mechanical changes as possible.

lib/Sema/DerivedConformanceCodingKey.cpp

@@ -214,7 +214,7 @@ deriveBodyCodingKey_enum_stringValue(AbstractFunctionDecl *strValDecl, void *) {
     for (auto *elt : elements) {
       auto *pat = new (C) EnumElementPattern(TypeLoc::withoutLoc(enumType),
                                              SourceLoc(), DeclNameLoc(),
-                                             DeclName(), elt, nullptr);
+                                             DeclNameRef(), elt, nullptr);
       pat->setImplicit();
 
       auto labelItem = CaseLabelItem(pat);