When the core/buttons block is registered, migrate from the coblocks/buttons block

[AnthonyLedesma]

Closes #1235
With the release of Gutenberg 7.2 a new buttons block has been introduced. The new core/buttons block seems to have conflicts with the coblocks/buttons block as shown in this screenshot.

Before

This PR adds logic to automatically convert the CoBlocks Buttons block to the Core Buttons block if available.

After

[mmtr]

This is looking good!

I wonder if it'd be good to make the CoBlocks Buttons block non-insertable, so users don't get confused about having 2 blocks with the same name on the inserter.

Gutenberg supports a inserter option in the supports block settings that can be used to prevent the block from being inserted while maintaining support for existing posts containing it.

[mmtr]

Seems this is not converting the Hero's Buttons child block. Likely because the new core/buttons block is not allowed:

coblocks/src/blocks/hero/edit.js

Line 33 in a66d386

const ALLOWED_BLOCKS = [ 'core/heading', 'core/paragraph', 'core/spacer', 'core/button', 'core/list', 'core/image', 'coblocks/alert', 'coblocks/gif', 'coblocks/social', 'coblocks/row', 'coblocks/column', 'coblocks/buttons' ];

[jrtashjian]

This is working well!

It would be nice to figure out a way to auto-transform our blocks into the Core versions so that we could minimize the amount of code left behind. But for this block we actually still need to keep this code around since the core/buttons block is not merged into WordPress Core yet.

This is a great method of deprecating our blocks to prefer the core versions and I'm looking forward to improving on this over time. Great work @AnthonyLedesma!