**What**
- Fixes an issue where the admin dashboard would send region prices for deleted regions.
- Also, includes the implementation for `GET /admin/shipping-options/:id` and its corresponding SDK function.
**Why**
- When a region price for a deleted region was sent to the backend it would result in the insert hitting a not null constraint on the currency_code for prices. To avoid this the dashboard should not send region prices for deleted regions.
**Additional context**
- Prices for deleted regions should ideally not be returned when fetching shipping option prices. However, we don't yet have a mechanism for cleaning up region prices after a region is deleted.
Fixes CC-540
**What**
- Renames /admin-next -> /admin
- Renames @medusajs/admin-sdk -> @medusajs/admin-bundler
- Creates a new package called @medusajs/admin-sdk that will hold all tooling relevant to creating admin extensions. This is currently `defineRouteConfig` and `defineWidgetConfig`, but will eventually also export methods for adding custom fields, register translation, etc.
- cc: @shahednasser we should update the examples in the docs so these functions are imported from `@medusajs/admin-sdk`. People will also need to install the package in their project, as it's no longer a transient dependency.
- cc: @olivermrbl we might want to publish a changelog when this is merged, as it is a breaking change, and will require people to import the `defineXConfig` from the new package instead of `@medusajs/admin-shared`.
- Updates CODEOWNERS so /admin packages does not require a review from the UI team.
