Gracefully truncate entity_path in audit_events

What does this MR do?

With the introduction of the new entity_path field and its length constraint (i.e. 5,500), we would like to ensure audit instrumentation trying its best to save this piece of information. When the length exceeds this length, we'd like to silently truncate the value and allow users to carry on with their main action.

Relates to #230430 (closed)

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
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Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

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• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
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