gh-109162: libregrtest: fix _decode_worker_job()

[vstinner]

Decode also HuntRefleak() object inside the RunTests object.

Add an unit test on huntrleaks with multiprocessing (-R -jN).

• Issue: Refactor test.libregrtest #109162

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @AlexWaygood for commit 833c6dc 🤖

If you want to schedule another build, you need to add the 🔨 test-with-refleak-buildbots label again.

[vstinner]

🤖 New build scheduled with the buildbot fleet by @AlexWaygood for commit 833c6dc 🤖

Oh, I tested the exact command used by buildbots locally and I validated that my change fix this command.

I also added an unit test to check for non-regression.

I merged my PR since I would like to create following pull requests which rely on this fix.

[AlexWaygood]

Oh, I tested the exact command used by buildbots locally and I validated that my change fix this command.

No worries! Some of the buildbots were already coming back green anyway, so I'm pretty confident we're okay here :-)

Thanks for the quick fix!

[vstinner]

I merged my PR since I would like to create following pull requests which rely on this fix.

Following PR: PR #109204.