fix: Capture Debug.LogError as message, not exception

[bitsandfoxes]

Depends on getsentry/sentry-dotnet#4681
Resolves #2334

Problem

The UnityApplicationLoggingIntegration receives stringified stack traces from Unity for log messages. The SDK automatically captures Debug.LogError events when CaptureLogErrorEvents is enabled. Previously, when AttachStacktrace was enabled, the SDK created a synthetic UnityErrorLogException to attach the stack trace to these events, which would then be processed as a normal exception.

This approach caused several issues:

• Incorrect event type: Debug.LogError messages appeared as exceptions on the Sentry dashboard, not as error messages
• Misleading severity: Issues were sometimes marked as fatal when they were just error logs

Proposal

Debug.LogError events are now captured as message events with stack traces attached via the SentryThreads property, following the same pattern as the MainEventProcessor uses (see here) for regular messages with AttachStacktrace enabled.

Result

[bitsandfoxes]

These are not new tests. The parsing was already tested in the UnityLogExceptionTests and now moved into the helper.