Fix ci-tests env generation, align with ci-locks.

[pp-mo]

Adopting the changes which appeared to be necessary for the ci-locks action in #470 :
Do the same to ci-tests.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.50%. Comparing base (792ba1e) to head (d23a0ec).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #481   +/-   ##
=======================================
  Coverage   90.50%   90.50%           
=======================================
  Files           6        6           
  Lines         811      811           
  Branches       93       93           
=======================================
  Hits          734      734           
  Misses         64       64           
  Partials       13       13           

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[pp-mo]

Ping @trexfeathers @bjlittle can we accept this now ?

Big 🥕 it also stops using conda-main !

[pp-mo]

Thanks @bjlittle !