Show "group" in multi-select toolbar

[jiteshdhamaniya]

Description

This PR solves this #34461 issue, add a Group Icon button to Multi Block Toolbar.

How has this been tested?

• Create Multiple Blocks
• Select Multiple blocks
• You will see Group icon in toolbar, click on it group them.

Screenshots

Types of changes

New feature

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR (please manually search all *.native.js files for terms that need renaming or removal).

[github-actions]

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[andrewserong]

Thanks for working on this @jiteshdhamaniya, I just happened to stumble on this PR while looking into the possibility of exposing this control. Very cool to see you've already explored this!

It's been a while since you opened the PR, are you keen to continue working on it? Not a worry at all if you currently don't have time to, but if so, it looks like it could use a rebase against trunk to get it up to date, and I'm happy to help out with testing / reviews.

[andrewserong]

It could be worth moving this slightly further down into its own ToolbarGroup to the right (visually) of the BlockMover, so that it's in its own section, in case we'd like to add other similar controls in the future?

[mtias]

Yes, this should be present in the actual block tools, not in the block type meta functions (transforms, movers, etc).

[andrewserong]

Thanks again for the work here @jiteshdhamaniya! I've opened up a new PR in #39710 borrowing your changes here, and have made a couple of small changes to deal with some edge cases.