Define requestedStorage per AppDefinition and not per Operator

[iyannsch]

The amount of allocated storage for persistent workspaces is configurable via operator.requestedStorage to be passed to the K8s PVC resource. Thus, every workspace regardless of its running AppDefinition will have the same amount of storage available.

But does every app have the same requirements in regard to storage?
We don't think so! While CPU, RAM, and even network usage are configurable on a AppDefinition level, the storage isn't.

***Proposal
Add requestedStorage to the parameters of an AppDefinition so that configurations like this become feasible:

requestsStorage: 250M

requestsMemory: 4800M
requestsCpu: 1000m
limitsMemory: 4800M
limitsCpu: "4"
downlinkLimit: 30000
uplinkLimit: 30000