❄️ Refactor cryostat geometry calculations into a new Cryostat class

[chris-ashe]

This pull request refactors the cryostat geometry calculations by moving them into a new dedicated Cryostat class. The changes also include code cleanup and removal of redundant methods. Here are the most important changes:

Refactoring and code organization:

• Moved cryostat geometry calculations to a new Cryostat class in process/cryostat.py.
• Updated process/main.py to initialize the new Cryostat class.
• Updated process/caller.py to call the run method of the new Cryostat class.

Code cleanup:

• Removed the external_cryo_geometry method from process/blanket_library.py and related calls. [1] [2]
• Removed the cryostat_output method and related calls from process/build.py. [1] [2]

These changes improve the modularity and readability of the code by encapsulating cryostat-related functionality within its own class.

Checklist

I confirm that I have completed the following checks:

• My changes follow the PROCESS style guide
• I have justified any large differences in the regression tests caused by this pull request in the comments.
• I have added new tests where appropriate for the changes I have made.
• If I have had to change any existing unit or integration tests, I have justified this change in the pull request comments.
• If I have made documentation changes, I have checked they render correctly.
• I have added documentation for my change, if appropriate.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 63.33333% with 11 lines in your changes missing coverage. Please review.

Project coverage is 31.74%. Comparing base (cf82f05) to head (b78bf24).

Files with missing lines	Patch %	Lines
process/cryostat.py	69.23%	8 Missing ⚠️
process/caller.py	0.00%	1 Missing ⚠️
process/main.py	50.00%	1 Missing ⚠️
process/output.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3594      +/-   ##
==========================================
+ Coverage   31.71%   31.74%   +0.02%     
==========================================
  Files          84       85       +1     
  Lines       20152    20161       +9     
==========================================
+ Hits         6392     6400       +8     
- Misses      13760    13761       +1     

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[timothy-nunn]

Much nicer structure, does not change any output, rename any variables, or cause any test issues