refactor: Replaced instances of substr() with substring()

[bizob2828]

Description

Most of the updates were clean. Only one that was referencing a negative index needed adjusted to work with substring.

How to Test

Please describe how you have tested these changes. Have you run the code against an example application?
What steps did you take to ensure that the changes are working correctly?

Related Issues

Closes NR-82088

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.32%. Comparing base (6c964b2) to head (06187b2).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2274      +/-   ##
==========================================
- Coverage   96.32%   96.32%   -0.01%     
==========================================
  Files         284      284              
  Lines       45178    45181       +3     
==========================================
+ Hits        43518    43520       +2     
- Misses       1660     1661       +1     

Flag	Coverage Δ
integration-tests-16.x	50.10% <14.28%> (-0.01%)	⬇️
integration-tests-18.x	49.23% <14.28%> (-0.01%)	⬇️
integration-tests-20.x	49.24% <14.28%> (-0.01%)	⬇️
unit-tests-16.x	89.17% <100.00%> (+<0.01%)	⬆️
unit-tests-18.x	89.16% <100.00%> (+<0.01%)	⬆️
unit-tests-20.x	89.16% <100.00%> (+<0.01%)	⬆️
versioned-tests-16.x	77.57% <50.00%> (-0.06%)	⬇️
versioned-tests-18.x	78.56% <50.00%> (-0.09%)	⬇️
versioned-tests-20.x	78.56% <50.00%> (-0.09%)	⬇️

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