Read fp_mask_{}.dat explicitely as float

[oczoske]

Positions for the pinhole in the METIS WCU focal-plane mask were given as (0, 0) in e.g. fp_mask_pinhole_lm.dat (in the irdb). The hole positions were then initialised as int. In combination with a shift argument given as float (e.g. 0.5) this caused an error since the shift is applied in-place via +=. This PR converts the entries in the mask table explicitely to float since that is the assumed data type for hole positions anyway.

Closes #868

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.88%. Comparing base (c4bd454) to head (780ec3d).
⚠️ Report is 122 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #869   +/-   ##
=======================================
  Coverage   74.88%   74.88%           
=======================================
  Files          69       69           
  Lines        8870     8870           
=======================================
  Hits         6642     6642           
  Misses       2228     2228           

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