Combine style-engine stores for block-supports

[aristath]

What?

Right now we have a separate store for layout-block-supports and generic block-supports.
The result is that on the frontend the CSS gets printed like this: (notice there are 2 separate <style> elements, each one with a different ID)

<style id='block-supports-inline-css'>
.wp-elements-c2d3692c067254e99911402d49af8a7d a {
	color: var(--wp--preset--color--background);
}

</style>
<style id='layout-block-supports-inline-css'>
.wp-block-navigation.wp-container-3 {
	justify-content: flex-end;
}
.wp-block-columns.wp-container-9 {
	flex-wrap: nowrap;
}
.wp-block-group.wp-container-4,.wp-block-query-pagination.wp-container-12,.wp-block-group.wp-container-14 {
	justify-content: space-between;
}
.wp-block-group.wp-container-5 > :where(:not(.alignleft):not(.alignright):not(.alignfull)),.wp-block-group.wp-container-6 > :where(:not(.alignleft):not(.alignright):not(.alignfull)),.wp-block-group.wp-container-10 > :where(:not(.alignleft):not(.alignright):not(.alignfull)),.wp-block-query.wp-container-13 > :where(:not(.alignleft):not(.alignright):not(.alignfull)),.wp-block-group.wp-container-15 > :where(:not(.alignleft):not(.alignright):not(.alignfull)),.wp-block-group.wp-container-16 > :where(:not(.alignleft):not(.alignright):not(.alignfull)) {
	max-width: 650px;
	margin-left: auto !important;
	margin-right: auto !important;
}
.wp-block-group.wp-container-5 > .alignwide,.wp-block-group.wp-container-6 > .alignwide,.wp-block-group.wp-container-10 > .alignwide,.wp-block-query.wp-container-13 > .alignwide,.wp-block-group.wp-container-15 > .alignwide,.wp-block-group.wp-container-16 > .alignwide {
	max-width: 1000px;
}
.wp-block-group.wp-container-5 .alignfull,.wp-block-group.wp-container-6 .alignfull,.wp-block-group.wp-container-10 .alignfull,.wp-block-query.wp-container-13 .alignfull,.wp-block-group.wp-container-15 .alignfull,.wp-block-group.wp-container-16 .alignfull {
	max-width: none;
}
</style>

This PR uses the block-supports store for layouts as well.
The result is this:

<style id='block-supports-inline-css'>
.wp-elements-c2d3692c067254e99911402d49af8a7d a {
	color: var(--wp--preset--color--background);
}
.wp-block-navigation.wp-container-3 {
	justify-content: flex-end;
}
.wp-block-columns.wp-container-9 {
	flex-wrap: nowrap;
}
.wp-block-group.wp-container-4,.wp-block-query-pagination.wp-container-12,.wp-block-group.wp-container-14 {
	justify-content: space-between;
}
.wp-block-group.wp-container-5 > :where(:not(.alignleft):not(.alignright):not(.alignfull)),.wp-block-group.wp-container-6 > :where(:not(.alignleft):not(.alignright):not(.alignfull)),.wp-block-group.wp-container-10 > :where(:not(.alignleft):not(.alignright):not(.alignfull)),.wp-block-query.wp-container-13 > :where(:not(.alignleft):not(.alignright):not(.alignfull)),.wp-block-group.wp-container-15 > :where(:not(.alignleft):not(.alignright):not(.alignfull)),.wp-block-group.wp-container-16 > :where(:not(.alignleft):not(.alignright):not(.alignfull)) {
	max-width: 650px;
	margin-left: auto !important;
	margin-right: auto !important;
}
.wp-block-group.wp-container-5 > .alignwide,.wp-block-group.wp-container-6 > .alignwide,.wp-block-group.wp-container-10 > .alignwide,.wp-block-query.wp-container-13 > .alignwide,.wp-block-group.wp-container-15 > .alignwide,.wp-block-group.wp-container-16 > .alignwide {
	max-width: 1000px;
}
.wp-block-group.wp-container-5 .alignfull,.wp-block-group.wp-container-6 .alignfull,.wp-block-group.wp-container-10 .alignfull,.wp-block-query.wp-container-13 .alignfull,.wp-block-group.wp-container-15 .alignfull,.wp-block-group.wp-container-16 .alignfull {
	max-width: none;
}
</style>

The <style> elements get combined and everything else remains the same.

The benefit of doing this is that as we convert all implementations to use the style engine, common selectors and declarations can be combined resulting in further optimizations of our styles. The more we add to the same store, the more it can be optimized.

[ramonjd]

Good call.

Now that we've solved the gutenberg_get_layout_style return value problem, this makes perfect sense.

Smoked tested in block and classic themes. LGTM!

[oandregal]

Added labels for the changelog.