Reducing functions issues due to azure storage limitations

Right now, it's pretty easy for users to shoot themselves in the foot with [Azure storage limitations](https://docs.microsoft.com/en-us/azure/azure-subscription-service-limits#storage-limits) by doing things like running multiple function apps referencing the same account for AzureWebJobsStorage.

We should either detect and notify users when being throttled or discourage users from getting into this situation in the first place.

A few ideas per @eduardolaureano

- Monitor storage usage and alert customers that they are getting to being throttled. Action item for the customer is to have function app in different storage accounts, I’d imagine this is a bit of a pain for the customer.
- We could warn at function app create time about storage account sharing to try to prevent a bad setup from the get-go.
- Control on how much we send to storage (if possible)