fix: Display dragged comments and bubbles atop the toolbox

[gonfunko]

The basics

• I validated my changes

The details

Resolves

Fixes #9537

Proposed Changes

This PR fixes two bugs with identical presentation:

• When workspace comments were dragged over the toolbox (to delete them), they appeared behind the toolbox. They were being added to the drag layer correctly, but on focus moved themselves to the block layer. Now, they just append themselves to their current parent on focus, which preserves the raise-on-focus behavior but also keeps them on whatever layer they're currently on, and thus correctly z-ordered.
• When blocks were dragged over the toolbox, their attached bubbles appeared behind the toolbox. Bubbles are not children of blocks in the DOM; they live on a separate, unrelated layer and were not being moved to the drag layer with their parent blocks. They now are.