Extract stacktrace builder into own utility class

What does this MR do and why?

This MR moves stracktrace builder logic from ErrorTracking::ErrorEvent model into its own utility class for easier testing and reuse.

See !90122 (diffs, comment 991438221)

Screenshots or screen recordings

Error details	Issue from error

How to set up and validate locally

1. Setup Sentry integration on your GDK instance
2. View error details which shows stacktrace
3. Create an issue from an error and view the issue which shows stacktrace

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.