Enable capacity growth with seed parameter

[dc2917]

Description

This PR enables the option to provide a seed parameter for capacity growth, as per #1424 (review).

• The csv reader looks for an optional growth_seed column
• If present, these values are then stored in a new growth_seed field of the ProcessInvestmentConstraintRaw struct.
• Simple input validation takes place to check that the values, if not None, are greater than or equal to 1, and finite.
  • Tests have been added for this validation
• The schema for process_investment_constraints.csv input files has been updated with details of this new parameter

Fixes #1425

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
• Update release notes for the latest release if this PR adds a new feature or fixes a bug
  present in the previous release

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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.91%. Comparing base (ef971c4) to head (968dff5).

Additional details and impacted files

@@                       Coverage Diff                       @@
##           add-capacity-growth-constraint    #1426   +/-   ##
===============================================================
  Coverage                           86.90%   86.91%           
===============================================================
  Files                                  59       59           
  Lines                                8391     8397    +6     
  Branches                             8391     8397    +6     
===============================================================
+ Hits                                 7292     7298    +6     
  Misses                                783      783           
  Partials                              316      316           

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