Fix github.ref check for concurrency settings (backport #453)

[mergify]

github.ref:

The ref given is fully-formed, meaning that for branches the format is refs/heads/<branch_name>.

which means the leading slash was wrong, see this canceled job for example.

https://docs.github.com/en/actions/reference/workflows-and-actions/contexts#github-context

I also added the concurrency settings for all other workflows.

---

This is an automatic backport of pull request #453 done by Mergify.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (humble@13356b3). Learn more about missing BASE report.

Additional details and impacted files

@@            Coverage Diff            @@
##             humble     #454   +/-   ##
=========================================
  Coverage          ?   59.11%           
=========================================
  Files             ?       28           
  Lines             ?     1541           
  Branches          ?      839           
=========================================
  Hits              ?      911           
  Misses            ?      243           
  Partials          ?      387           

Flag	Coverage Δ
unittests	59.11% <ø> (?)

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