Fix missing line numbers in CaptureMessage stacktraces in IL2CPP builds

[tustanivsky]

Closes #1509

[github-actions]

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

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

- Fix missing line numbers in `CaptureMessage` stacktraces in IL2CPP builds ([#1567](https://github.com/getsentry/sentry-unity/pull/1567))

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 4a27123

[munkiki7]

Latest findings:

• if you use the il2cpp API functions to get the current thread stacktrace frames (il2cpp_current_thread_get_stack_depth and iterate using il2cpp_current_thread_get_frame_at)

the call is successful only for the lowest frame (less meaningful);

• the method name and function address look valid using the c++ to c# struct mapping for the valid frame;

• the actual frames are only captured for the messages sent on Unity UI interactions (by other event processors);

• even for the only valid frame we still could not extract the info like on the image above (module and package).