[openacc][openmp] Allow duplicate between required and allowed once/exclusive

[openacc][openmp] Allow duplicate between required and allowed once/exclusive

Validity check introduce in D90241 are a bit too restrict and this patch propose to losen
them a bit. The duplicate clauses is now check only between the three allowed lists and between the
requiredClauses and allowedClauses lists. This allows to enable some check where a clause can be
required but also appear only once on the directive. We found these kind of restriction useful
on the set directive in OpenACC for example.

Reviewed By: kiranchandramohan

Differential Revision: https://reviews.llvm.org/D90770