Apply IDE refactoring suggestions

[martincostello]

Cherry-pick code refactoring/modernisation from #3252.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 83.56%. Comparing base (1433ce6) to head (eb03984).
⚠️ Report is 339 commits behind head on master.

Files with missing lines	Patch %	Lines
...ggerGen/SchemaGenerator/OpenApiSchemaExtensions.cs	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3254      +/-   ##
==========================================
- Coverage   83.56%   83.56%   -0.01%     
==========================================
  Files          76       76              
  Lines        3225     3224       -1     
  Branches      559      559              
==========================================
- Hits         2695     2694       -1     
  Misses        530      530              

Flag	Coverage Δ
Linux	83.56% <92.85%> (-0.01%)	⬇️
Windows	83.56% <92.85%> (-0.01%)	⬇️
macOS	83.56% <92.85%> (-0.01%)	⬇️

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