[OpenMP][NFCI] Move OpenMP clause information to `lib/Frontend/OpenMP`

This is a cleanup and normalization patch that also enables reuse with
Flang later on. A follow up will clean up and move the directive ->
clauses mapping.

Reviewed By: fghanim

Differential Revision: https://reviews.llvm.org/D77112
diff --git a/clang/lib/AST/TextNodeDumper.cpp b/clang/lib/AST/TextNodeDumper.cpp
index dc0dd92..2933457 100644
--- a/clang/lib/AST/TextNodeDumper.cpp
+++ b/clang/lib/AST/TextNodeDumper.cpp
@@ -314,7 +314,7 @@
   }
   {
     ColorScope Color(OS, ShowColors, AttrColor);
-    StringRef ClauseName(getOpenMPClauseName(C->getClauseKind()));
+    StringRef ClauseName(llvm::omp::getOpenMPClauseName(C->getClauseKind()));
     OS << "OMP" << ClauseName.substr(/*Start=*/0, /*N=*/1).upper()
        << ClauseName.drop_front() << "Clause";
   }
@@ -1534,7 +1534,8 @@
       }
       {
         ColorScope Color(OS, ShowColors, AttrColor);
-        StringRef ClauseName(getOpenMPClauseName(C->getClauseKind()));
+        StringRef ClauseName(
+            llvm::omp::getOpenMPClauseName(C->getClauseKind()));
         OS << "OMP" << ClauseName.substr(/*Start=*/0, /*N=*/1).upper()
            << ClauseName.drop_front() << "Clause";
       }