Page List allows insertion of any child block

[getdave]

Whilst testing the auto inserted Page List in the Nav block we noticed it's possible to insert any block type within the Page List block itself.

Screen.Capture.on.2022-12-01.at.10-55-54.mp4

Page List should only allow core/page-list-item.

[scruffian]

There are a few different ways that users can add blocks to the Page List block:

1. I can add page list as a child of page list using the appender
2. I can drag and drop some blocks into the block.

We need to make sure these things are also not possible.