(core) Customizable stripe plans.

Summary:
- Reading plans from Stripe, and allowing Stripe to define custom plans.
- Storing product features (aka limits) in Stripe, that override those in db.
- Adding hierarchical data in Stripe. All features are defined at Product level but can be overwritten on Price levels.
- New options for Support user to
-- Override product for team site (if he is added as a billing manager)
-- Override subscription and customer id for a team site
-- Attach an "offer", an custom plan configured in stripe that a team site can use
-- Enabling wire transfer for subscription by allowing subscription to be created without a payment method (which is customizable)

Test Plan: Updated and new.

Reviewers: georgegevoian

Reviewed By: georgegevoian

Differential Revision: https://phab.getgrist.com/D4201

stubs/app/server/server.ts

@@ -90,7 +90,7 @@ async function setupDb() {
       }, {
         setUserAsOwner: false,
         useNewPlan: true,
-        planType: TEAM_FREE_PLAN
+        product: TEAM_FREE_PLAN
       }));
     }
   }