fix: Defensive coding and exception handling during ASP.NET Core 6+ browser injection

[tippmar-nr]

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Description

Adds more defensive coding and exception handling during ASP.NET Core 6+ browser agent injection. Also adds an integration test to validate that we're handling responses that don't set a ContentType header.

Resolves #2035

Author Checklist

• Unit tests, Integration tests, and Unbounded tests completed
• Performance testing completed with satisfactory results (if required)

Reviewer Checklist

• Perform code review
• Pull request was adequately tested (new/existing tests, performance tests)

[codecov-commenter]

Codecov Report

Merging #2038 (a5da07f) into main (ca96d0c) will decrease coverage by 0.03%.
Report is 1 commits behind head on main.
The diff coverage is 75.86%.

@@            Coverage Diff             @@
##             main    #2038      +/-   ##
==========================================
- Coverage   81.07%   81.05%   -0.03%     
==========================================
  Files         394      394              
  Lines       24667    24672       +5     
  Branches     2962     2962              
==========================================
- Hits        20000    19998       -2     
- Misses       3883     3889       +6     
- Partials      784      785       +1     

Files	Coverage Δ
...serMonitoring/BrowserScriptInjectionIndexHelper.cs	82.25% <75.86%> (-5.47%)	⬇️

... and 4 files with indirect coverage changes