Standardise constraint residual/normalised residual calculations

[timothy-nunn]

Standardises how we calculate normalised residuals and errors for constraints for our three types of constraints: geq, eq, leq

[codecov-commenter]

Codecov Report

❌ Patch coverage is 87.50000% with 26 lines in your changes missing coverage. Please review.
✅ Project coverage is 46.62%. Comparing base (ac78fdb) to head (aa68eee).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
process/constraints.py	87.50%	26 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4066      +/-   ##
==========================================
+ Coverage   46.60%   46.62%   +0.02%     
==========================================
  Files         122      122              
  Lines       28711    28645      -66     
==========================================
- Hits        13381    13356      -25     
+ Misses      15330    15289      -41     

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