Add subscription_id to service principal json

**Is your feature request related to a problem? Please describe.**

Since `--sdk-auth` is now deprecated from `az ad sp create-for-rbac` it's expected to use the original json output when creating a service principal. However, the json that's output is completely different. There's two issues:

- The key names are all different (This is not good from a compatibility standpoint but it's easy to handle)
- The subscription_id is missing (This is not nice because then it requires all SDK calls to provide the subscription)

**Describe the solution you'd like**

Given service principals are tied to a specific subscription it would be helpful for the subscription_id to be added to the original json output. This would be helpful in terms of compatibility for users who relied on the `--sdk-auth` option.

**Describe alternatives you've considered**

Keep `--sdk-auth` option

**Additional context**

No