Buttons Block should have Color, Border, Style, etc Controls (overridable per button)

[MadtownLems]

What problem does this address?

If I have a Buttons group of several identical looking buttons (which I imagine is a pretty common situation), and want to make a change to them, I currently need to manually update each and every Button individually. This can be very time consuming.

What is your proposed solution?

The Buttons block could/should have various controls that impact all descendent Buttons by default, but still allow individual buttons to override them. (Similar to how a Group block can have Color settings that cascade down to descendant blocks but can be overridden.)

[justintadlock]

This is related to #38267, which proposes adding a method to update adjacent button styles. Leaving this open since it's a proposal for a slightly different approach. But, we can close in favor of the other.

Also see: #27324