Meta Description Generator: Post Admin Component

### Description

>[!TIP]
>[Meta Description Generator feature reference document for Alley devs](https://l.alley.dev/0e3715e20a)

Set up a component for posts that allows editors to generate (or re-generate) meta descriptions.

The component should always appear, even if the meta description is populated. If it is already populated, the editor will be able to replace it.

By default, the component should display on all public posts (of any post type enabled for use with this plugin) with `show_ui` true. We should allow this value to be filterable (this same functionality is used in the CLI command component).

### Use Case

When an editor would like to generate (or re-generate) a meta description for a post, they should be able to do so within the post editor.