Remove favorite button block, use shared block

[ryelle]

This removes the favorite block in favor of the new shared favorite button. Unlike https://github.com/WordPress/wporg-theme-directory/pull/148, I did not remove the favorite endpoints here — they're not bundled with the theme, and while I don't think they're used anywhere else, I wanted a second opinion before just pulling them out.

See https://github.com/WordPress/wporg-mu-plugins/discussions/617

To test

• Use the branch here https://github.com/WordPress/wporg-mu-plugins/pull/635
• Make sure to build both projects
• View the pattern directory
• There should be small heart icons on each pattern in the grid, with counts
• If you are logged in, those are clickable; if not, they're just text
• View a single pattern
• You should see a button in the theme header with a count
• If you are logged in, it should be are clickable; if not, it's just text
• You should be able to click or trigger with a keyboard to favorite/unfavorite items, and the button should update with the interaction
• Reload the page or view /favorites to ensure the favorite saved correctly

[adamwoodnz]

Updated my local env to test this, but was initially blocked because the parent theme wasn't installed. I think we need to add it to composer.json 🙂

[colorful-tones]

Updated my local env to test this, but was initially blocked because the parent theme wasn't installed. I think we need to add it to composer.json 🙂

I opened #701 to try and address this.