Add per entity permission checks to Notification Test endpoint

[ryan-carroll-graylog]

Description

Adds entity-level permission check to event notification test endpoint which is the same checks that the /events/notifications/{notificationId}/test uses.

Motivation and Context

Closes: https://github.com/Graylog2/graylog-plugin-enterprise/issues/14753

How Has This Been Tested?

Verify that a user cannot test a notification they do not have edit permission for.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have requested a documentation update.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[danotorrey]

LGTM and tests successfully.