Add dead time backend

[mdoucet]

Add dead time correction to the backend calculations

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 22.44898% with 76 lines in your changes are missing coverage. Please review.

Project coverage is 35.07%. Comparing base (1e4e8be) to head (5dbf175).

Files	Patch %	Lines
..._ui/interfaces/data_handling/DeadTimeCorrection.py	23.21%	43 Missing ⚠️
...ectivity_ui/interfaces/data_handling/instrument.py	13.51%	32 Missing ⚠️
...flectivity_ui/interfaces/data_handling/data_set.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             next      #81      +/-   ##
==========================================
- Coverage   35.28%   35.07%   -0.21%     
==========================================
  Files          30       31       +1     
  Lines        6054     6149      +95     
==========================================
+ Hits         2136     2157      +21     
- Misses       3918     3992      +74     

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