Move time slice CSV code to input submodule

[alexdewar]

Description

This PR moves the time slice CSV code to a submodule of input, as we've done for all the other modules now. This is the last bit of refactoring related to #281.

No functional changes.

Closes #288. Closes #281.

Type of change

• Bug fix (non-breaking change to fix an issue)
• New feature (non-breaking change to add functionality)
• Refactoring (non-breaking, non-functional change to improve maintainability)
• Optimization (non-breaking change to speed up the code)
• Breaking change (whatever its nature)
• Documentation (improve or add documentation)

Key checklist

• All tests pass: $ cargo test
• The documentation builds and looks OK: $ cargo doc

Further checks

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[codecov]

Codecov Report

Attention: Patch coverage is 95.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 95.68%. Comparing base (b8d9fe8) to head (5c99247).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
src/input/time_slice.rs	95.00%	3 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #345      +/-   ##
==========================================
- Coverage   95.71%   95.68%   -0.03%     
==========================================
  Files          27       28       +1     
  Lines        3223     3224       +1     
  Branches     3223     3224       +1     
==========================================
  Hits         3085     3085              
- Misses         61       62       +1     
  Partials       77       77              

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[dalonsoa]

This looks ok. Just to confirm, there's no functional change, just moving things around, right?

[alexdewar]

This looks ok. Just to confirm, there's no functional change, just moving things around, right?

Yep, exactly