Remove All specific alignment CSS from block based themes and replace them with layout confings

[youknowriad]

Now that this PR https://github.com/WordPress/gutenberg/pull/29335 landed on Gutenberg. Any theme with an experimental-theme.json will be impacted.

Here are the changes that need to be made for these themes If they do support "wide/full" alignments:

• Remove the old theme support flag.
• Remove all alignments CSS from your theme's CSS files.
• Define the default "layout" config in theme.json (this is going to be used as a default layout style for the post editor). and update the FSE templates to inherit the default layout where necessary.

Follow #233 as an example of how to do that