Update the WordPress packages with Gutenberg 15.1.0 changes

[youknowriad]

This PR updates the WordPress packages with the latest released ones from Gutenberg 15.1.0

While updating the packages, it was necessary to bring the following changes as well:

• React upgrade to 18.2.0
• iframe the block theme editor. (Related PRs Block editor: iframe for block based themes (PHP backport) #3904, Block editor: separate content styles for the iframe (PHP backport) #3903 )

Trac ticket: https://core.trac.wordpress.org/ticket/57471

[Mamaduka]

I noticed that we have a few methods with the gutenberg_ prefix in the block-library packages. I'm looking into this.

[felixarntz]

@youknowriad Mostly looks good, just one nit-pick and the remaining gutenberg_ prefixes that need to be replaced. Is that something you can just update in this PR or does it require a fix on the Gutenberg side?

Other than that, I assume the intention is to commit this once #3920 has been committed?

[Mamaduka]

@felixarntz, I already fixed gutenberg_ prefix issue in Gutenberg repo. See WordPress/gutenberg#47649.

@ntsekouras and I will start working on package updates that include recent fixes.

[youknowriad]

Mostly looks good, just one nit-pick and the remaining gutenberg_ prefixes that need to be replaced. Is that something you can just update in this PR or does it require a fix on the Gutenberg side?

Actually, I can't touch these files here, even the nitpicks suggested here because every time someone will do npm install it will revert these changes locally causing confusion. So I think we should instead make a PR to Gutenberg and wait for the next round of package release.

[youknowriad]

I've just noticed that there's a blocks fixtures tests in Core right now. Anyone know why this test has been moved from Gutenberg to here? It's just going to add maintenance burden for us for a small value since all the code for blocks is coming through package. In other words, these tests are better by their code (in the Gutenberg repo).

[youknowriad]

Ok I've managed to fix all the failing tests here. It's not perfect but It should be good to land to unblock the PRs that depend on it.

I've noticed a small style glitch on the empty post placeholder. Something to keep an eye on after all the backports.

[felixarntz]

@youknowriad LGTM. Would still be nice to address https://github.com/WordPress/wordpress-develop/pull/3914/files#r1095179123, though that is not a blocker.

[youknowriad]

@felixarntz It needs to be addressed on Gutenberg, that way it comes in the next package update. You can't make changes to these files in Core.

[felixarntz]

@youknowriad Ah right, forgot about that, thanks!

[ntsekouras]

LGTM to land this. Thank you Riad!

[youknowriad]

This has been committed

[Mamaduka]

Thank you, Riad!

The changeset - https://core.trac.wordpress.org/changeset/55246.