Event definitions paging does not account for visibility

## Expected Behavior

Paging should be consistent with what is visible to the user.

## Current Behavior

Paging is based on all event definitions. But when you click beyond what the user can access you just get a blank page.
See #18998 for screenshots.

## Context

Not blocking anything, but confusing.

## Your Environment

* Graylog Version: 6.0 RC4