feat: non-nullable privacy setting

[vaind]

This suggests a change on top of another PR (#2361) - I think it would be more user-friendly to provide the options.experimental.privacy as a non-nullable field so users can set its properties directly.

See code comments for some more details

[github-actions]

	Fails
🚫	Please consider adding a changelog entry for the next release.

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

Instructions and example for changelog

Please add an entry to CHANGELOG.md to the "Unreleased" section. Make sure the entry includes this PR's number.

Example:

## Unreleased

- non-nullable privacy setting ([#2382](https://github.com/getsentry/sentry-dart/pull/2382))

If none of the above apply, you can opt out of this check by adding #skip-changelog to the PR description.

Generated by 🚫 dangerJS against a82a879

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.08%. Comparing base (57a0823) to head (a82a879).

Additional details and impacted files

@@                              Coverage Diff                               @@
##           feat/redact-screenshots-via-view-hierarchy    #2382      +/-   ##
==============================================================================
+ Coverage                                       84.93%   85.08%   +0.14%     
==============================================================================
  Files                                              81       81              
  Lines                                            2808     2809       +1     
==============================================================================
+ Hits                                             2385     2390       +5     
+ Misses                                            423      419       -4     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.