Indicate Sentry error level in GitLab

What does this MR do?

Changes level badge color based on error severity

Screenshots

Whole page

Severity badges

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

References #39075 (closed)