Add reading of calibration files in fits format

[FrancaCassol]

This is necessary in order to move to fits output as requested by EvB

[codecov]

Codecov Report

Attention: Patch coverage is 42.30769% with 30 lines in your changes missing coverage. Please review.

Project coverage is 89.67%. Comparing base (247104c) to head (2c919ba).

Files with missing lines	Patch %	Lines
src/ctapipe_io_lst/calibration.py	42.30%	30 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #238      +/-   ##
==========================================
- Coverage   90.97%   89.67%   -1.30%     
==========================================
  Files          25       25              
  Lines        2637     2674      +37     
==========================================
- Hits         2399     2398       -1     
- Misses        238      276      +38     

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