chore: Add custom cmake definitions for gersemi

[mathbunnyru]

High Level Overview of Change

This adds definitions for our custom functions/macros, and they format nicely too by gersemi.

Context of Change

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Performance (increase or change in throughput and/or latency)
• Tests (you added tests for code that already exists, or your new feature included in this PR)
• Documentation update
• Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• Release

API Impact

• Public API: New feature (new methods and/or new fields)
• Public API: Breaking change (in general, breaking changes should only impact the next api_version)
• libxrpl change (any change that may affect libxrpl or dependents of libxrpl)
• Peer protocol change (must be backward compatible or bump the peer protocol version)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.8%. Comparing base (5865bd0) to head (4c36e6c).
⚠️ Report is 1 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #6491   +/-   ##
=======================================
  Coverage     79.8%   79.8%           
=======================================
  Files          861     861           
  Lines        67858   67858           
  Branches      7573    7552   -21     
=======================================
+ Hits         54147   54176   +29     
+ Misses       13711   13682   -29     

see 9 files with indirect coverage changes

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