Buttons Block: Add a way to control button padding

[alaczek]

It would be useful to have padding controls for individual buttons. We recently added font-size controls, which is a great start, but having padding controls would give us full creative freedom independent of the theme. This would be especially useful when the theme is setting large padding on buttons by default making it impossible to create smaller, compact buttons.

Here's an example from the Seedlet theme.
If I wanted to create a button like this:

it would not be possible, because the theme sets default button padding at 23px. So even if I adjusted font-size, it would look like this:

Somewhat related to: #29098

[paaljoachim]

I am pinging @aaronrobertshaw about this issue. As he is currently working on associated padding/margin dimension controls.

[aaronrobertshaw]

Thanks for the ping @paaljoachim.

@stacimc has done some great work on adding the padding support to buttons in #31774. I believe we just need to give that a final review then it shouldn't be far off landing. I'll find some time in the coming days to give it a test.

[apeatling]

Axial padding support is now in place for the buttons block. #33859