Rename `Gitlab::Sentry` into service-agnostic `Gitlab::ErrorTracking`

What does this MR do?

In !17819 (merged) we renamed the methods of the Gitlab::Sentry class.

Gitlab::Sentry does not reflect the purpose of the class and we need more generic, service-agnostic name.

This is intended to be just a renaming MR (since it touches many files), all functional / logic changes should be addressed in other MRs to ease the process of the review.

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

Availability and Testing

N/A

Security

N/A

Related to #38332 (closed)