Fix SA1602/S6608/S4144 warnings

[gintsk]

The issue or feature being addressed

Contributes to #1290

Details on the issue fix or feature implementation

Fix SA1602
Fix S6608 (net481 style)
Fix S4144 (remove duplicate tests)

Confirm the following

• I started this PR by branching from the head of the default branch
• I have targeted the PR to merge into the default branch
• I have included unit tests for the issue/feature
• I have successfully run a local build

[gintsk]

@dotnet-policy-service agree

[martincostello]

Thanks!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (19b5e73) 84.81% compared to head (317b244) 84.81%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1936   +/-   ##
=======================================
  Coverage   84.81%   84.81%           
=======================================
  Files         312      312           
  Lines        6900     6900           
  Branches     1056     1056           
=======================================
  Hits         5852     5852           
  Misses        839      839           
  Partials      209      209           

Flag	Coverage Δ
linux	84.81% <ø> (ø)
macos	84.81% <ø> (ø)
windows	84.81% <ø> (ø)

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