Fix Site Editor close button for G v11.9

[Addison-Stavlo]

Changes proposed in this Pull Request

With Gutenberg v11.9, the navigation toggle was removed. This caused our override to close the editor to no longer work, thus the editor in 11.9 now tries to close to wp-admin instead of calypso, which is not allowed and results in this gray screen:

Here, we add the selector for the new close button to keep the same override functionality. Once v12.0 is shipped to dotcom, we can get rid of this hacky goo altogether and go back to using the slot/fill for overriding the close button.

Testing instructions

• Patch this diff to your sandbox
• On a non-edge site, open the site editor and verify closing behavior is unchanged.
• Patch D69833-code to your sandbox to enable the new entry point.
• On an edge site, open the site editor and verify closing leads back to calypso.

Related to #

[matticbot]

This PR modifies the release build for editing-toolkit

To test your changes on WordPress.com, run install-plugin.sh editing-toolkit fix/site-editor-close-button-override-11.9 on your sandbox.

To deploy your changes after merging, see the documentation: PCYsg-mMA-p2

[github-actions]

Link to Calypso live: https://calypso.live?image=registry.a8c.com/calypso/app:commit-b24804132fdf4a0ad726046a65d1e45885527d22
Link to Jetpack Cloud live: https://calypso.live?image=registry.a8c.com/calypso/app:commit-b24804132fdf4a0ad726046a65d1e45885527d22&env=jetpack
(These links may take a few minutes to be available)

[matticbot]

This PR does not affect the size of JS and CSS bundles shipped to the user's browser.

Generated by performance advisor bot at iscalypsofastyet.com.

[fullofcaffeine]

Curious about this:

Once v12.0 lands, we should be able to use a slotfill and get rid of this entire file.

Does that mean there's a fix for this in core that was introduced and scheduled for v12.0?

[creativecoder]

@fullofcaffeine yes, see WordPress/gutenberg#36369

[Addison-Stavlo]

It looks like that fix is being cherry picked into 11.9. We may need to update things as we are currently filling that slot for its previous context of being inside the nav sidebar and wrapping the < Dashboard button.