Added scripts/run_molecule_parallel.py to run a runner's assigned
(scenario, platform) pairs in parallel. If any subprocess fails, the
remaining ones are terminated with SIGTERM/SIGKILL and the runner
exits immediately. This gives fast feedback without continuing to run
tests that are guaranteed to fail for the same reason.
CI workflow now calls this script per matrix runner. Added fail-fast and
max-parallel for best-effort cancellation across runners.
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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>