Move Gallery "Add new / Media Library" actions to the Toolbar

[mtias]

Right now we have a trailing appender on the Gallery block which is a bit problematic — it only allows inserting new images or editing the gallery if you are at the bottom of it. On large galleries that requires scrolling. We should move these controls to the toolbar instead, which scrolls with the user.

[paaljoachim]

Visuals.

Here is what it looks like for single images.

That means having somewhat similar controls for the gallery in the toolbar as exist for single image blocks.

[dwolfe]

Is this all we need? ("Current media URL" wouldn't apply at the level of the gallery.)

@mtias, should we keep the bar at the bottom with (now duplicate) Upload and Media Library buttons, or do you envision the controls at the top replacing them?

[mtias]

I'd hope we can replace them initially. Eventually gallery items will be blocks and we could use the actual inserter.

[paaljoachim]

Gallery items will likely become nested image blocks inside a parent gallery.
That means something like this: #11436 (comment)

[MichaelArestad]

@dwolfe Perhaps a + icon would be more fitting than "Add" in that toolbar. I also would remove the dropdown actions in favor of just opening the media modal. What do you think?

[dwolfe]

@MichaelArestad:

1. Why do you think a + icon would be more successful than an explicit label?
2. What advantage does opening the media modal have, over the dropdown actions?

[dwolfe]

In the interest of moving this forward, I think the word "Add" is clearer than an icon, and it reuses the "Replace" pattern from the image block toolbar. Also, the dropdown surfaces the option to upload a new image more clearly than the Media Library's "Add New" button, which has to compete visually with a thumbnail grid; so I think the dropdown (which also aligns with the "Replace" control) is a better compromise than immediately opening the Media Library.

I think this is good enough for now, and we can iterate based on any feedback we get once it's merged.

[dwolfe]

Updated comp incorporating @mtias' feedback above:

To summarize:

• Removes the trailing appender
• Introduces an "Add" button with a text label (see: image block "Replace" button)
• "Add" button invokes a dropdown menu with "Open Media Library" and "Upload" options (see: image block "Replace" button, but omit "Current Media URL" item)

NOTE: This is a temporary fix, given that the Gallery block will at some point transition to a nested block architecture as @paaljoachim mentioned above.