Need frame counts for tomography dose weighting

[stephen-riggs]

Adds frame count finding for tomography, and passes this on to the processing.
Storing the frame count requires a database change, so we may not want to merge this change immediately.

[codecov]

Codecov Report

Attention: Patch coverage is 33.33333% with 4 lines in your changes missing coverage. Please review.

Project coverage is 27.30%. Comparing base (12e96fe) to head (5294b5b).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #469   +/-   ##
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  Coverage   27.30%   27.30%           
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  Files          78       78           
  Lines       10164    10169    +5     
  Branches     1338     1338           
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+ Hits         2775     2777    +2     
- Misses       7293     7296    +3     
  Partials       96       96           

[tieneupin]

Just one comment about kV, but otherwise looks ok