Experimental: Remove styles from template parts

[carolinan]

Description
This is a test for "Remove color, spacing, and layout options for Template Part block" WordPress/gutenberg#36571

Screenshots

Testing Instructions
Provide steps for testing

1. Apply Remove color, spacing, and layout options for Template Part block gutenberg#36571
2. (Make sure you remove any saved template or template part changes from the install)
3. View the editor and front. Test both the default header, and the two dark headers.

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Known issues:

• A bottom padding below the header was removed on 404
• There are spacing inconsistencies between the default header and the two black headers, on smaller screen widths.
• Footer and header patterns are untested.

[kjellr]

Thanks for getting this started, @carolinan! I pushed a couple small fixes for these items:

• A bottom padding below the header was removed on 404
• There are spacing inconsistencies between the default header and the two black headers, on smaller screen widths.

As for the patterns, I expect that a few of them might need adjustments, but that can be handled separately. I think this PR is ready for when/if WordPress/gutenberg#36571 lands. 👍

[kjellr]

WordPress/gutenberg#36571 has been merged upstream, so I'll merge this in too. Thank you!