This commit moves all of the PHP code from `plugins/woocommerce-admin`
to its new home in `plugins/woocommerce`.
- `plugins/woocommerce-admin/src` -> `plugins/woocommerce/src/Admin`
- `plugins/woocommerce-admin/src-internal` -> `plugins/woocommerce/src/Internal`
- `plugins/woocommerce-admin/includes` -> `plugins/woocommerce/includes/react-admin`
* Add psr-4 for the internal classes -- this is a temp. changes. We should remove it once we completely merge to the core
* Register class aliases
* Move WcPayPromotion classes to the internal
* Ignore namespace PHP CS issue
* Make features/WcPayPromotion internal
* Added src-internal directory for Automattic\WooCommerce\Internal\Admin namespace
* Moved src/Features/WcPayPromotion to src-internal/Admin/WcPayPromotion
* Add phpcs rules for src-internal
* Remove phpcs:ignoreFile
* Update letter case to make it PSR4 compatible
* Fix letter cases
* Move the alias array into the function
* Rename WcPayPromotion to WCPayPromotion (letter case update)
* Include src-internal
* Update letter case
* Make classes internal
* Update references
* Fix WC_ADMIN_ABSPATH path
Christopher Allford
Moon
Jeff Stieler
Adrian Duffell