Gutenberg: Group Block: add ability to alter padding values

[getdave]

The Section Block currently has padding added when a background color is set. It would be good to be able to adjust this setting regardless of whether there is a background color set.

Describe the solution you'd like
A UI to enable the adjusting of the Block inner padding. This should

• Allow pixel level adjustment of the Block padding
• Allow adjustment of the 4 values independently of each other or as a single value

Potential Considerations

• What should happen with different viewport sizes? For exmaple a large padding that looks great on large screens would look terrible on small screens. How do we handle this?

[youknowriad]

I think there's already an issue about this (related to responsive controls), this might be a duplicate.

[paaljoachim]

I would think that the Group block could go ahead as an example on how to add block specific padding/margin controls. Getting it in place so that down the line it could also be added to other blocks.

I am adding in some issues.

Block-specific responsive controls

13363

Add padding and margin for blocks, and get rid of Spacer block.
https://github.com/WordPress/gutenberg/issues/11824

Add Block: Responsive

6650

Support for Responsive Columns

6048

[mtias]

I like starting with this block to see how specific controls might work.

[getdave]

@mtias I've started work on an implementation of this.

[mapk]

I'm removing the Needs Design label because it looks like the design work in happening in the PR.

[mtias]

@ItsJonQ could we look at enabling the padding control from _Cover_ here?