[clang][TypePrinter] Honour SuppressTagKeyword in non-canonical TagType path

LLVM's behaviour may be right:

Explicitly-written keywords should be preserved.

It is simpler to have this downstream patch than handle all the cases
in ROOT/Cling manually.

Possibly fix the failing tests on Windows:

- roottest-root-io-withoutDictionaries-IOWithoutDictionaries
- roottest-root-io-withoutDictionaries-RowWiseNoProxyWarning
- roottest-root-tree-stl-mixingInterp
- roottest-root-tree-stl-mixingCompiled

Need to revisit previous commits added to fix this issue.

Author: devajithvs

interpreter/llvm-project/clang/lib/AST/TypePrinter.cpp

@@ -1526,7 +1526,8 @@ void TypePrinter::printTagType(const TagType *T, raw_ostream &OS) {
       OS << ' ';
     }
   } else {
-    OS << TypeWithKeyword::getKeywordName(T->getKeyword());
+    if (!Policy.SuppressTagKeyword)
+      OS << TypeWithKeyword::getKeywordName(T->getKeyword());
     if (T->getKeyword() != ElaboratedTypeKeyword::None) {
       PrintedKindDecoration = true;
       OS << ' ';