Consider adding a plugin option to enable experimental block controls

[kjellr]

What problem does this address?

There are a number of block features that themes may opt-into via theme.json. For example:

"settings": {
	"color": {
		"link": true
	},
	"border": {
		"customColor": true,
		"customRadius": true,
		"customStyle": true,
		"customWidth": true
	},
	"spacing": {
		"customPadding": true
	},
	"typography": {
		"customFontSize": true,
		"customLineHeight": true
	}
}

When trying to test using the plugin, it's difficult to keep track of which themes support which features. I often go looking for one of these settings, only to find it's not opted into in my current theme. This requires me to either edit my theme's code, or go digging around to figure out what other theme does opt in. This also means it's hard to stay on top of new controls as they're added to the plugin — they won't show up for testers without an extra step in the theme they're using.

What is your proposed solution?

Would it be feasible to include a plugin-only checkbox to opt-in to all of these settings at once, regardless of your current theme? We already have an "Experimental settings" panel, and it seems like that would be a great place for this control.