Change display to a trait

[jlenain]

This PR proposes to change display in SPEalgorithm to a trait, which should hopefully answer to #224.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 51.27%. Comparing base (f004eef) to head (15d905c).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #228      +/-   ##
==========================================
- Coverage   51.79%   51.27%   -0.52%     
==========================================
  Files          78       78              
  Lines        6505     6541      +36     
==========================================
- Hits         3369     3354      -15     
- Misses       3136     3187      +51     

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[pcorcam]

Hi @jlenain,

Thanks for taking care of this enhancement! The new display_toggle trait works as expected when adding it to the configuration of a FlatFieldSPENominalNectarCAMCalibrationTool and child classes.

Although I approve all current changes, I did find some very minor display keyword-argument syntax in two lines of spe_algorithm.py; see the comment on that file. Could you please have a look before I approve the review? Thanks!