- The `Container` class now implements `Psr\Container\ContainerInterface`
(and registers itself as such), holding a private instance of the
real container. This way it's a read-only container from the point
of view of plugins (which should use their own containers, but
can still use this to get WooCommerce classes).
- All registrations are now done in the `Container` constructor via
service providers.
- The container instance is now held in a global variable, set in
`woocommerce.php`
- Added the `wc_get_container` function for old code.
- Added the `AbstractServiceProvider` class, which inherits with the
corresponding League's class and adds some utility methods,
most notably `add/shareWithAutoArguments`.
- Added the `ActionsProxy` and `LegacyProxy` classes, they are
registered via a dedicated service provider.
- `WC_Queue_Interface` is no longer resolvable via the container
(which is for classes inside `src` only).
- All the method names in the new classes have the format `fooBarFizz`
to be PSR4 compliant, so the MethodNameInvalid error has been
disabled in phpcs.xml for the `src` directory.
- Introduced the `@public` annotation for public API classes
(classes that plugins can use and whose backwards compatibility
we guarantee), applied to `ActionsProxy` and to `LegacyProxy` for now.
- Removed the hack for the autoloader as now it doesn't work anyway.
For the changes in this branch to work, now WP_DEBUG must be false.