Resolve IP address from RequestContext for audit

What does this MR do?

Resolve IP address from RequestContext for audit event.

Before this MR, to correctly instrument audit event, the callers have to pass on the request IP address. These classes do not always have access to IP address (e.g. Service classes). In addition, acquiring this piece of information should not be the responsibility of the callers.

In this MR, we push the responsibility to resolve IP address to the AuditEventService. IP address can be retrieved from RequestContext and injected directly on AuditEventService. This approach helps keeping the interface to AuditEventService smaller and be more user-friendly.

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

• 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

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] 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
• [-] Security reports checked/validated by a reviewer from the AppSec team

Related to #239305 (closed)