Social Icons: Move color options to block toolbar

[jasmussen]

In #28084, social icons landed the ability to change foreground and background colors of icons.

This happens in the sidebar, but it's such a useful action, it should happen in the toolbar. Like this, perhaps:

This mockup is inspired by this original design, but expanded with a little influence from #27331.

[carolinan]

Is this still something we want to implement?

[jasmussen]

The design is a bit out of date, but in my mind it still makes sense to do this, including for other blocks where the color plays a prominent role, such as Cover.

[jasmussen]

I'll close this for now. As out of date as the visuals are, let's revisit separately.