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 63.33%. Comparing base (47f963d) to head (8c731c2).
Report is 28 commits behind head on main.

❗ There is a different number of reports uploaded between BASE (47f963d) and HEAD (8c731c2). Click for more details.

HEAD has 3 uploads less than BASE

Flag	BASE (47f963d)	HEAD (8c731c2)
	4	1

Additional details and impacted files

@@             Coverage Diff             @@
##             main      #13       +/-   ##
===========================================
- Coverage   97.33%   63.33%   -34.01%     
===========================================
  Files           8        8               
  Lines         525      540       +15     
===========================================
- Hits          511      342      -169     
- Misses         14      198      +184     

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[Oisin-M]

Closing as this is merged into #20