Fibre transmission for WCU lasers

[oczoske]

Add fibre transmission for the METIS WCU lasers. The value is defined in AstarVienna/irdb#334

If needed, it can be changed with

wcu.fibre_trans = 0.5
wcu.set_lamp("laser")    # needed to recompute the emergent intensity
metis.observe()

The figure shows the effect for five different values on the ImagePlane, where the thermal background has been subtracted.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.11%. Comparing base (63c3876) to head (281e04e).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #904      +/-   ##
==========================================
+ Coverage   74.81%   75.11%   +0.30%     
==========================================
  Files          69       69              
  Lines        8948     8953       +5     
==========================================
+ Hits         6694     6725      +31     
+ Misses       2254     2228      -26     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[teutoburg]

LGTM