Zoom Out: Prevent nested patterns when in zoom out

[scruffian]

What problem does this address?

Generally we expect that patterns are sectioning elements for pages. Consequently we should prioritise adding patterns between other patterns rather than allowing them to be nested.

What is your proposed solution?

We should prevent users from nesting patterns inside other patterns when in zoom out mode.

To make it possible to still add nested patterns, we will need to ensure that #63861 is done before this issue. ✅ It's done.