[OpenMP][NFC] Move and simplify directive -> allowed clause mapping

Move the listing of allowed clauses per OpenMP directive to the new
macro file in `llvm/Frontend/OpenMP`. Also, use a single generic macro
that specifies the directive and one allowed clause explicitly instead
of a dedicated macro per directive.

We save 800 loc and boilerplate for all new directives/clauses with no
functional change. We also need to include the macro file only once and
not once per directive.

Depends on D77112.

Reviewed By: JonChesterfield

Differential Revision: https://reviews.llvm.org/D77113

Author: jdoerfert

clang/include/clang/ASTMatchers/ASTMatchers.h

@@ -7119,7 +7119,7 @@ AST_MATCHER(OMPDefaultClause, isSharedKind) {
 /// ``isAllowedToContainClauseKind("OMPC_default").``
 AST_MATCHER_P(OMPExecutableDirective, isAllowedToContainClauseKind,
               OpenMPClauseKind, CKind) {
-  return isAllowedClauseForDirective(
+  return llvm::omp::isAllowedClauseForDirective(
       Node.getDirectiveKind(), CKind,
       Finder->getASTContext().getLangOpts().OpenMP);
 }