feat: Expose StringOrRegex discriminator

[limbonaut]

Exposes whether a StringOrRegex contains a literal string or a regular expression through a new public discriminator. This allows SDK integrations to preserve trace propagation target semantics across interop boundaries without reflection or treating regex patterns as literal strings.

• Refs feat(dotnet): Sync trace propagation options sentry-godot#916

The Godot SDK reads these targets from the .NET SDK and passes them to its native layer. Without this discriminator, it cannot tell a plain string from a regex. Reflection is not an option because Godot supports AOT on iOS, while treating regex patterns as strings would be incorrect.

[limbonaut]

Can’t tag you for review, so I’ll just ping you, @jamescrosswell and @Flash0ver 🙂

[jamescrosswell]

Thanks @limbonaut - Generally OK with the change but I think we could simplify it. I don't think we need to add a new enum to do what you want.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.70%. Comparing base (6c51ea5) to head (7d1ec8e).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5543      +/-   ##
==========================================
- Coverage   74.72%   74.70%   -0.02%     
==========================================
  Files         515      515              
  Lines       18948    18949       +1     
  Branches     3696     3696              
==========================================
- Hits        14158    14156       -2     
- Misses       3906     3910       +4     
+ Partials      884      883       -1     

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