Clean up /extensions code and refactor them into its proper places

## Description

We copied the label printing react components into WCS&T from Calypso (https://github.com/Automattic/woocommerce-services/pull/1655) so that our changes in WCS&T will not impact Store.

Store is no longer a blocker and we have started removing Calypso (https://github.com/Automattic/woocommerce-services/issues/2333). Once Calypso is removed, we should revisit this whole `woocommerce-services/client/extensions` folder and see if we can:

- Delete un-used components/files
- Refactor the file structure
- Consider using WP/ WC components instead of `woocommerce-services/client/extensions`.

Start by auditing the woocommerce-services/client/extensions folder and the label-printing React components copied from Calypso. Review issue #2333 and the existing WordPress/WooCommerce component usage before deciding which files are unused or misplaced. Done means the folder is reduced or reorganized and appropriate WordPress/WooCommerce components replace local ones where applicable.

Written by the indexing model from the issue text.