Block Themes: Add section styling via extended block style variations
Provide users with the ability to style entire sections of a page without
having to tediously reapply the same sets of styles.
This is done by extending block style variations to apply to nested blocks.
See https://github.com/WordPress/gutenberg/pull/57908.
Fixes #61312.
Props aaronrobertshaw, talldanwp, ramonopoly, isabel_brison, andrewserong.