Refactor fetcher

[mraspaud]

This PR refactors trollmoves to use the pytroll-watchers url handling and fetching in the background.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.55%. Comparing base (492cd85) to head (19efc8a).
Report is 23 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #214      +/-   ##
==========================================
- Coverage   91.72%   91.55%   -0.18%     
==========================================
  Files          28       28              
  Lines        5666     5587      -79     
==========================================
- Hits         5197     5115      -82     
- Misses        469      472       +3     

Flag	Coverage Δ
unittests	91.55% <100.00%> (-0.18%)	⬇️

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