V8: Allow all content types at root if none are explicitly allowed

[kjac]

Prerequisites

• I have added steps to test this contribution in the description below

If there's an existing issue for this PR then this fixes: #4414

Description

#4414 calls for allowing all content types at the root if none are explicitly marked as "Allow as root". This PR fixes that.

Testing this PR

This PR affects both content and media and the test steps below should be repeated for both content and media.

1. Make sure that nothing is broken 😄 in other words test that if any content types are marked as "Allow as root" you can't create, move or copy any other content types to root.
2. Disable "Allow as root" on all content types.
3. Verify that you can create all content types at root.
4. Verify that you can move and copy all content types to root - also from the recycle bin.

[warrenbuckley]

All tested & reads fine. Thanks again @kjac 🎉