Storage version change for subscriptions.messaging.dev

[aliok]

Problem
Make the stored version for subscriptions v1 and provide migration job.

This was done in #3925 but then realized that subscription reconciler is not using v1 shape, so needed to revert the changes for subscriptions.

The revert commit is in the same PR.

Persona:
Which persona is this feature for?

Exit Criteria
A measurable (binary) test that would indicate that the problem has been resolved.

Time Estimate (optional):
How many developer-days do you think this may take to resolve?

Additional context (optional)
Add any other context about the feature request here.