Use "Design" panel for Query Loop block

[richtabor]

I propose that we update the Query Loop block to the existing "Design" Inspector panel UI/UX, rather than the "Replace" modal that is currently in place. This would bring the experience to match what is currently in place for header and footer template parts, and also reduce confusion for the "Replace" control, which is used on media block toolbars.

The "Design" panel may need to be closed by default.

Visual

[richtabor]

For reference, here's the existing UI for template parts to reuse: