Add message for admins to indicate what action would happen

FYI in Field Redirection we display this message to admins:

This page is set to redirect to another URL, but you have permission to see this page and will not be automatically redirected.

Thank you @DamienMcKenna once again, just ran into exactly the same idea! Once again hero of the day and +1 here!

I really like the idea and support of adding this feature to 2.0.x version.

I'll submit an MR with the proof of concept shortly. The next steps would be:
1) Decide on what level it would be configured. Possible options: a) global (save in rabbit_hole.settings); b) bundle (save in rabbit_hole.behavior_settings.*). Also, keep in mind ✨ Add option to apply rabbit hole behaviors to all users including administrators Fixed as both features are mutually exclusive if they're applied globally.

2) Add configuration option and adjust conditions;

3) Decide on the message wording. It should look good and clear for all available actions, potentially including custom ones.

Current message:

This page is set to apply "@action" action, but you have permission to see this page.

Possible actions: "Page not found", "Access Denied", "Page redirect".

4) Add test coverage.

Adding screenshots to the issue description

1) There is a new checkbox, saved in the bundle settings;
2) Done;
3) Suggestions/improvements will be accepted in the follow-up issue;
4) Done.

Thank you!

Automatically closed - issue fixed for 2 weeks with no activity.