Add support for Data Access Configuration for Azure redis

**Related command**
`az redis`

**Is your feature request related to a problem? Please describe.**
I'm trying to set up an Azure redis cache using the CLI. I can do most things, but for the data access policies, I need to resort to the UI/Azure Portal, which is painful for many users

**Describe the solution you'd like**
- Add a user with Owner policy: `az redis data-access add --user foo@bar.com --policy 'Data Owner'`
- List all users, their access policies, and usernames: `az redis data-access show`
- Query the user ID of a specific user: `az redis data-access show --user foo@bar.com`

**Describe alternatives you've considered**
There is no commandline alternative, I can only use the Azure portal