Track nil `proxy` to Sentry upon field access

What does this MR do?

In #36801 (closed) we identified the need to make load balancer proxy late-init failures more explicit by logging an appropriate error to Sentry whenever proxy is attempted to be accessed before it had been configured. Access will still fail-fast due to the proxy being nil.

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

I'm not sure how to test this -- since this is an EE feature, I suspect I need a particular license that I need to fake in development?