[OpenMP] New/derived taskgraph tests
This patch adds new tests for 'omp taskgraph' functionality, but (unlike
the patches posted in PR66919) leave the existing tests using the internal
runtime API for record and replay as-is.
I have changed the 'print_dot' tests to use FileCheck instead of their
own internal checking, though.
Co-authored-by: Adrian Munera <adrian.munera@bsc.es>
