Allow spacing in typography variations

[richtabor]

As a follow-up to #60220, I propose we allow for spacing to be allowed within typography variations.

This would allow typography variations to be much more refined, as the space between paragraphs (spacing.blockGap) may be modified by a typography variation, as well as adjustments for elements like buttons—which may need more padding with an accompanying larger font size.

Visual

Here's a visual of the current typography variations, which are filtered from theme style variations:

[richtabor]

Marking this as a bug, as blockGap cannot be expressed by typography variations to set the space between paragraphs.

[mtias]

I think we have to be careful to muddle typography presets with potentially unrelated spacing changes. The fundamental issue seems to be we need some better control over spacing between paragraphs that can also account for whether a heading is preceding. Also related to #37462

If these are typography specific settings they would be available in the typography key.

[ellatrix]

This is an enhancement, so punting to WP 6.7.

[justintadlock]

Just throwing this out there: I'd also argue that layout width, specifically settings.layout.contentWidth, is directly tied to typography. Outside of font-size this is the best way to adjust for characters per line.

[mtias]

It might be worth exploring expressing content width with ch units as well as a possible default.