GalleryBlock: place edit button in separate toolbar.

[mtias]

Fixes #1129.

@jasmussen do you want to add the proper icon?

[jasmussen]

Nice!

Like @njpanderson, we should use the edit icon here. That's what the current gallery uses also.

[jasmussen]

I dig it! Works well. 👍

[aduth]

Two things:

• We created BlockControls (and later similarly InspectorControls) as abstractions to obscure the underlying fill behavior and naming. We should decide whether this is a pattern we want to embrace and apply it consistently.
• On the point of consistency, while perhaps out of scope of this pull request, seems we should move all controls to be rendered as descendants of the edit component.

[youknowriad]

On the point of consistency, while perhaps out of scope of this pull request, seems we should move all controls to be rendered as descendants of the edit component.

Agree, That was my intention after merging #1019

[paaljoachim]

This is really picky but I feel there is too much space between the icons in the toolbar:

Here is one that shows the two groups closer together.

I believe all toolbars that have groupings should have a less space between the groups.