[Fonts API] enqueue programmatically fonts picked in block settings

[zaguiini]

What problem does this address?

Picking a programmatically registered font in the block settings does not enqueue it, unless it's been allow-listed in theme.json[settings][fontFamilies].

What is your proposed solution?

We need to introspect block settings on render and look for font families. Once a family is found, and that font is registered, enqueue it.

Blockers

We only want to work on this after #40362, so only a subset of programmatically registered webfonts show up in the block settings.

[hellofromtonya]

Hmm, I think this issue is not an issue after #40362 gets resolved.. Why? The intent is to populate typography pickers with only enqueued fonts.