Reusable blocks: Don't show trashed blocks in the editor or frontend

[noisysocks]

Fixes #12339.

Changes the logic surrounding reusable blocks so that we:

• Do not render a reusable block in the editor if it is trashed.
• Do not render a reusable block on the frontend if it is non-published or password protected.

This matches one's intuition about what Trashing something does.

Testing

1. Create a new post
2. Insert a block
3. Convert the block to a reusable block
4. Go to Manage All Reusable Blocks
5. Trash the reusable block you created
6. Go back to the post you created. The reusable block should appear as Deleted or unavailable
7. Preview the post. The reusable block should not appear

[youknowriad]

Should we match the check in the backend (status publish and no password)?

[noisysocks]

My thought was that having it this way would allow for some advanced functionality, e.g. marking a reusable block as private means that it becomes an editor only block.

After considering it some more, I think you're right. Let's keep it simple for now and we can enable more advanced functionality in future releases if needed.

I've updated the check.