[clang][OpenMP] 6.0: Add default clause support for 'target' directive (#162910)
Per OpenMP 6.0 specification, section 7.5.1, default Clause
Page 224, lines 3-5 default Clause, Semantics
If data-sharing-attribute is shared then the clause has no effect
on a target construct; otherwise, its effect on a target construct is
equivalent to specifying the defaultmap clause with the same
data-sharing-attribute and variable-category.
Testing:
OpenMP LIT tests
check-all