Geant4Output2EDM4hep: get run from worker context

[andresailer]

This will need some more work, the current status writes one run per thread.

BEGINRELEASENOTES

• Geant4OutputAction: In multithreaded mode, make sure the ingested run parameters end up in the output, fixes OutputAction and contexts #1660

ENDRELEASENOTES

[github-actions]

Test Results

   16 files     16 suites   9h 31m 6s ⏱️
  376 tests   367 ✅ 0 💤  9 ❌
2 657 runs  2 642 ✅ 0 💤 15 ❌

For more details on these failures, see this check.

Results for commit 130bce7.

[tmadlener]

the current status writes one run per thread.

I'm assuming a "trivial" solution employing std::call_once doesn't do the trick? Might be a bit trickier if there are multiple runs as well as multiple threads...