Switch Actions organization from ecmwf-actions to ecmwf

[recmanj]

Update CI/CD workflows as ecmwf-actions actions have been moved to ecmwf organization.

[FussyDuck]

All committers have signed the CLA.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 6.72%. Comparing base (c232820) to head (4200898).

Additional details and impacted files

@@           Coverage Diff           @@
##           develop      #8   +/-   ##
=======================================
  Coverage     6.72%   6.72%           
=======================================
  Files           23      23           
  Lines          863     863           
  Branches        60      60           
=======================================
  Hits            58      58           
  Misses         805     805           

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