[flang][openmp] - depend clause support in target, target enter/update/exit...

[flang][openmp] - depend clause support in target, target enter/update/exit data constructs (#81610)

This patch adds support in flang for the depend clause in target and
target enter/update/exit constructs. Previously, the following line in a
fortran program would have resulted in the error shown below it.

    !$omp target map(to:a) depend(in:a)


"not yet implemented: Unhandled clause DEPEND in TARGET construct"