Fix: Global styles for non-core blocks aren't loaded on the front end

[t-hamano]

Fix #43679

What?

This PR fixes that global styles for non-core blocks aren't loaded on the front end,

Why?

I think this is due to the fact that non-core blocks were excluded in wp_add_global_styles_for_blocks.

How?

I have applied the logic of script handle generation in the WordPress core.
This will ensure that global styles for non-core blocks and global styles for the elements property of non-core blocks are output correctly.

Testing Instructions

• Checkout this branch and build gutenberg.
• run npx @wordpress/create-block gutenpride outside gutenberg repository.
• Define the following in .wp-env.override.json.

{
	"plugins": [ ".", "../path/to/gutenpride" ],
}

• run npm run wp-env start -- --update
• Activate Gutenpride plugin.
• Activate the emptytheme and put the following code in theme.json.

{
	"$schema": "https://schemas.wp.org/trunk/theme.json",
	"version": 2,
	"styles": {
		"blocks": {
			"create-block/gutenpride": {
				"border": {
					"width": "3px",
					"color": "#f00",
					"style": "solid"
				},
				"color": {
					"text": "#fff",
					"background": "#000"
				},
				"elements": {
					"button": {
						"color": {
							"text": "#fff"
						}
					}
				}
			}
		}
	}
}

• Open the post editor.
• Insert the Gutenpride block and confirm that the style is applied.

Global styles should be output via the block handle on the front-end

• Confirm that the global style is generated inside the block handle (create-block-gutenpride-style-inline-css) on the front end.

Global styles should be output via the global-styles handle on the front-end

• Add add_filter( 'should_load_separate_core_block_assets', '__return_false' ); in functions.php.
• Confirm that the global style is generated inside the global handle (global-styles-inline-css) on the front end.

[t-hamano]

I think to check only slashes is the only way to include non-core blocks, is there a better approach?

[t-hamano]

The GitHub action failing will be resolved if #44052 is merged.

[scruffian]

I did something very similar here! #44018

[t-hamano]

Sorry, I should have checked my past PRs.
I would like to close this PR.