Shadow support enable skip serialization for dynamic blocks

[colinduwe]

What?

When a dynamic block defines __experimentalSkipSerialization in its block.supports.shadow the styles continue to be printed to the block wrapper element. This PR corrects that behavior so that shadow behaves like border, color, and others.

Why?

This provides the expected behavior for dynamic blocks that need to opt out of having the shadow styles printed to the block wrapper.

How?

Added a check at the start of the render function to return an empty array of the block has set __experimentalSkipSerialization

Testing Instructions

1. Choose a core dynamic block such as core/post-featured-image or create a dynamic block for testing
2. Add shadow to the block supports in block.json
3. Build the block
4. Add the block in a post and verify that the shadow styles are printed on the block wrapper
5. Update shadow to include "__experimentalSkipSerialization": true
6. Rebuild the block
7. Update the post and verify that the shadow styles are not printed on the block wrapper

There is a risk of a deprecation/regression so also check the core blocks that already support shadow

1. core/button
2. core/column
3. core/columns
4. core/image
   Core/image uses __experimentalSkipSerialization so verify that there is no change in the editor or front end with this PR.
   These are not dynamic blocks so should be unaffected by this change.

[github-actions]

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[github-actions]

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[colinduwe]

@aaronrobertshaw Here's a PR for improving the /supports/shadow as discussed at #59616

[aaronrobertshaw]

Thanks for splitting this out @colinduwe 👍

This is testing well for me. I used the dynamic Cover and Post Featured Image blocks for the majority of testing.

✅ Code change looks good
✅ Dynamic blocks that don't skip serialization still get styles on their wrapper
✅ Dynamic blocks that do skip serialization no longer get styles on the wrapper
✅ Static blocks continue to function correctly

LGTM 🚢

I'll merge this PR for you shortly.

The next step is to backport this PHP change to WordPress Core to be included in the WP 6.5 release. Is that something that you'd like to do?

There's some documentation available on how to do that and you can ping me in case you need a little help.

[colinduwe]

Thanks @aaronrobertshaw! Here's an attempt at the backport https://core.trac.wordpress.org/ticket/60784#ticket

[youknowriad]

This seems like an enhancement (add support for skipping serialization) to a new block support. So not really a regression or bug fix, so I'm removing the backport label (this needs to land in 6.6)

[aaronrobertshaw]

Happy to go with your call on this one 👍

I still see this as a bug given the support for skipping serialization was added in #58306 which lands in GB 17.7 & WP 6.5. If a consumer tries to use that for a dynamic block, as the block.json schema indicates is available, it won't work without this fix.

That said, I appreciate it can be argued that "support for dynamic blocks" is the enhancement.