Editor: add support for layout responsive styles.

Adds support for setting responsive layout, block spacing and child layout styles.

Props isabel_brison, ramonopoly, audrasjb, desrosj, sabernhardt.
Fixes #65164.


git-svn-id: https://develop.svn.wordpress.org/trunk@62478 602fd350-edb4-49c9-b593-d223f7449a82

Author: tellthemachines