Convert data directories to a list by removing the role

[stephen-riggs]

The role is now redundant as we only use the detector, and the presence of logic around the use of the microscope now causes problems in tomography.

This removes the role entirely, which means the data_directories can become a list rather than a dictionary.

[codecov]

Codecov Report

Attention: Patch coverage is 30.43478% with 16 lines in your changes missing coverage. Please review.

Project coverage is 27.83%. Comparing base (f99070b) to head (7810e26).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #412      +/-   ##
==========================================
+ Coverage   27.77%   27.83%   +0.06%     
==========================================
  Files          72       72              
  Lines        9883     9842      -41     
  Branches     1318     1305      -13     
==========================================
- Hits         2745     2740       -5     
+ Misses       7044     7012      -32     
+ Partials       94       90       -4     

[tieneupin]

Very thorough job. It looks like all instances of data_directories and role were caught.