Button Block: Removes "Link settings" panel

[Mamaduka]

Description

Fixes #23768 by removing the "Link Settings" panel and moving the "Link rel" field into advanced controls.

How has this been tested?

Using wp-env package.

Screenshots

Types of changes

• Removes part of the UI.
• Moves field into different controls area.

Checklist:

• My code is tested.
• My code follows the WordPress code style.
• My code follows the accessibility standards.
• I've tested my changes with keyboard and screen readers.
• My code has proper inline documentation.
• I've included developer documentation if appropriate.
• I've updated all React Native files affected by any refactorings/renamings in this PR.

[github-actions]

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[skorasaurus]

Thanks for your PR.
This also partially fulfills #20208 (comment)

I also checked if the community documentation needs to be updated and fortunately, the community documentation is out of date and uses the old button block instead of the new 'buttons' block which includes this.

I did some very basic tests

(create new page, add button - create a link for it; toggle the 'open in new tab' to be active' in the LINK url UI (not in the sidebar),
add an additional link rel value in the panel (e.g. external), click save;
and it looks good to me.

[Mamaduka]

Thanks for testing this @skorasaurus.

[ntsekouras]

Looks good!

Thanks for working on this @Mamaduka 💯 and congrats on your first GB PR! Really appreciated!

[Mamaduka]

Thanks, @ntsekouras for the review and for restarting the tests.