sagemathgh-40107: Add retry mechanism for Conda environment setup in CI workflow
    
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Sometimes the conda setup fails due to network issues (e.g. https://gith
ub.com/sagemath/sage/actions/runs/15036287079/job/42258557067?pr=38872#s
tep:9:7341). There is no easy way to configure conda to just retry this
request again in a few seconds, so we just simply retry the whole conda
env setup.

### :memo: Checklist

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preview.

### :hourglass: Dependencies

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URL: sagemath#40107
Reported by: Tobias Diez
Reviewer(s): Dima Pasechnik