ci: don't fail-fast sharded test execution

[mmat11]

Currently when there's a flaky test in a shard, the whole matrix gets canceled. This PR allows continuing the test execution for the other shards

/cc @skl

[skl]

Yes, no harm in this - thanks! Though I think only maintainers can actually re-run failed jobs.

[mmat11]

I think only maintainers can actually re-run failed jobs

I think approvers can do that, I just restarted a job in #755 , I found no way to restart another single shard after restarting a failed one or restart all failed shard tho :/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.20%. Comparing base (885e4c3) to head (a874af1).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #762      +/-   ##
==========================================
- Coverage   71.28%   71.20%   -0.08%     
==========================================
  Files         238      238              
  Lines       25168    25168              
==========================================
- Hits        17940    17922      -18     
- Misses       6349     6368      +19     
+ Partials      879      878       -1     

Flag	Coverage Δ
integration-test	58.02% <ø> (-0.03%)	⬇️
integration-test-arm	33.69% <ø> (-0.58%)	⬇️
k8s-integration-test	49.88% <ø> (-0.01%)	⬇️
oats-test	39.16% <ø> (-0.49%)	⬇️
unittests	46.79% <ø> (-0.02%)	⬇️

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