Add padding controls to core/latest-comments

[pbking]

Is your feature request related to a problem? Please describe.
In order to fully support the Latest Comment Style in TT1-blocks regarding the Global Style Editor the Latest Comments block should support padding controls.

Describe the solution you'd like

• The support.spacing.padding value set on the block to allow Block Editor to control padding values.
• The BoxControlVisualizer added to the block's 'edit' module so the spacing can be visualized.

[carolinan]

I am not sure if we want to do this?
It may be solved by https://github.com/WordPress/gutenberg/pull/29402/files,
because this is what the style in Twenty Twenty-One overrides.