Decouple buttons

[eoigal]

Changes proposed in this Pull Request

• The PR will try to decouple the login and subscribe buttons used in the non-subscriber view in the premium content block

Ref: #41850

I plan to use recent changes to block context to allow nested blocks to know what the container's selected plan ID is so it can be used to determine if those blocks should be rendered or not.

Testing instructions

• Apply PR and make sure sync'd with sandbox.
• Go to test FSE site (that is sandboxed).
• Test adding a premium content block to a post.
• Test that the buttons are rendered ok in the editor and in the published post.
• Test that you can remove all buttons and add them again inside the logged out (non-subscriber) view - you shouldn't be able to add a Premium content button to the subscriber view OR outside the Premium content container.

[matticbot]

Test live: https://calypso.live/?branch=decouple-buttons

[matticbot]

Caution: This PR affects files in the FSE Plugin on WordPress.com
Please ensure your changes work on WordPress.com before merging.

D43956-code has been created so you can easily test it on your sandbox. See this FieldGuide page about developing in the FSE Plugin for more info: PCYsg-ly5-p2

[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.