What?

This PR refactors the control used by the block variations transforms section in the block editor to use the ToggleGroupControl component instead of the custom components it is using at present.

Why?

As suggested in #43415, this update should reduce code duplication and make the component more accessible by default.

How?

I refactored the code to rely on a ToggleGroupControl inside a wrapper div that uses the existing block-editor-block-variation-transforms class. If we have unique icons for each variation, we insert ToggleGroupControlOptionIcon children, but if we don't we insert ToggleGroupControlOption children.

Testing Instructions

1. Open a Post or Page.
2. Insert a Group block (or any other block that includes variations)
3. Ensure that the Block controls are visible.
4. Verify that the block variation transforms control is visible and shows all the variations for the current block. If you have a Group, Row, or Stack block, you should see icons for the Group, Row, and Stack blocks, with the current block variation shown as selected
5. Verify that you see "Transform to " tooltips when you hover over the icons for the alternate block variations (i.e. not the current variation
6. Verify that you see the current block type as the tooltip (e.g. Row) when you hover over the selected block type
7. Select the other variations, and verify that the block type is correctly updated

Screenshots or screencast