Bring your own private DNS zone from another subscription doesn't work

[xaviermignot]

Describe the bug
When create a private cluster using an existing private DNS zone, the zone has to be in the same subscription as the cluster.
I have forked the repo and made a change in my environment, so I'm creating this issue to submit my changes in a PR.

To Reproduce
Steps to reproduce the behavior:

1. Follow the steps to create a private cluster, and select the "bring your own private DNS zone" option
2. Enter the resource id of a private DNS zone in a different subscription
3. Submit the deployment
4. You should get an error in the DNS RBAC module saying that the DNS zone can't be found

Expected behavior
If the resource id of the DNS zone is in another subscription, it should be found and the RBAC and VNET link should be set accordingly.

Screenshots
N/A

Additional context
N/A