Wp-calypso: Billing Management: Add subscription detail components to new site level routes (3)

[michaeldcain]

• add site-level route under /purchases/subscriptions/:site-id/:receipt-id
• Ensure auto-renew toggle still works
• Ensure renew works as well
• Cancel flows
• Change payment method
• need to verify that all linked pages have appropriate routes at the site level and/or modals

[sirbrillig]

1/3 of this is done in https://github.com/Automattic/wp-calypso/pull/45922

We still need to add:

• Cancel page
• Add payment method page
• We may also want to consider the thank-you page after a renewal completes

[sirbrillig]

The 2nd third is done in https://github.com/Automattic/wp-calypso/pull/45974 which handles the cancel page.

[nbloomf]

Part 3 (add/change payment method) is in #45977

[sirbrillig]

Part 4 (the cancel domain confirmation page) is in https://github.com/Automattic/wp-calypso/pull/46021