Improving zoom out with patterns

[jeryj]

The layout for Zoom Out mode when the pattern inserter is open could be quite improved. This issue will be referenced by several PRs working towards making the zoom out mode with pattern inserter flow accessible and smooth.

Context

Engaging the zoom-out Gutenberg experiment with the inserter open causes the pattern categories to overlap over the content. It's difficult to add patterns if you can't see where you're adding them.

Other improvements would be to have the patterns inserter remain open when inserting patterns (like it does outside of zoom-out mode), as well as consider improving the pattern quick inserter when in this view.

Note that this UI already exists in the form of a Gutenberg experiment. I am proposing refining this experimental view.

Related to #50739 and #39281.

co-authored with @richtabor

[richtabor]

@jeryj I think we can consider this closed by #59342 and #59337, with follow-ups on the zoom-out overview issue. Good work!