- Disables all configuration options for post content
- Disables anchor for FSE templates. Enables custom class name so we can
  inject the correct classname for the header/footer

This means that you can't see any reference to their settings!

Note that we cannot do this same patch for the post content
block because once the block has been disabled, you can't
edit the inner blocks. Will have to find a different patch for that.

Since users can see this in a few places, we want to make
sure they aren't confused when it does pop up.