[Flang][OpenMP] Fix 'Internal: no symbol found' for OpenMP aligned and linear clause.
The initial approach was to go with changing parser nodes from std::list<parser::Name> to OmpObjectList, but that might have lead to illegal programs.
Resolving the symbols inside OmpAttributeVisitor.
Fix a couple of XFAIL tests.
Reviewed By: kiranchandramohan
Differential Revision: https://reviews.llvm.org/D90538