[usage] Decouple billing controller from usage controller

[easyCZ]

Fix up how we trigger the sending of the usage report into Stripe. Currently it's done inside the ReconcileTimeRange This currently causes tests to report
[ERROR] Request error from Stripe (status 401): {"status":401,"message":"You did not provide an API key.
What we want is something akin to a pipeline.
Generate the report and return it. This completes the usage controller "data munching"
(later) Store it.
Pass it onto a Billing Controller.
In practice, it should be possible to succeed the usage report, but fail the Stripe update (for example for Stripe outage reasons)

[easyCZ]

Investigating this further, the easiest seems to actually introduce the following Services and RPCs:

1. UsageService.CollectUsage()
2. BillingService.UpdateInvoices()
   These two are then responsible for performing the respective parts of the control loops, can be invoked remotely but in the common case, are invoked periodically by the cron in the controller.

Doing so also gives us a couple of benefits:

1. Improved observability of either task, as we can piggy back on gRPC observability
2. When we need to sync explicitly, we can do so over an RPC
3. Makes it possible to in the future decouple the RPC trigger from the implementation - k8s cron

How would this actually look like?

• billing.proto - https://github.com/gitpod-io/gitpod/pull/11631/files#diff-82630443ae7d5700a98e48b4aeaf4b6ecbc55c2156f639e58aa64cb92bda934bR1
• usage.proto - https://github.com/gitpod-io/gitpod/pull/11631/files#diff-02538d53a95c532babc3fba3868ed35d20f3625383b5886e360fa48947db87b9L9

[easyCZ]

This is now complete.