[Shipping labels] Integrate print label action into UI layer in Woo Shipping flow

[rachelmcr]

In WooShippingPostPurchaseView, we need to print the label when the print button is tapped. This should:

• Dispatch the action to fetch the label data from remote for the selected paper size.
• Present the system print controller with the fetched data.

We might be able to reuse some or all of the logic in PrintShippingLabelCoordinator for this.

Note: Per the discussion in Slack (p1732618862774319-slack-C02KUCFCSFP) we are not using the default paper size set in the store; that will be implemented in a later milestone. For now we only need to handle the paper size selected in the UI.

[dangermattic]

Thanks for reporting! 👍