Allow generation of stable but unique name for resources

**Is your feature request related to a problem? Please describe.**
Generating globally unique names for resources that require a (globally unique) dns entry is challenging. In ARM templates, I would use the [uniqueString](https://docs.microsoft.com/en-us/azure/azure-resource-manager/templates/template-functions-string#uniquestring) function, seeding it with the "name" of the storage account (and possibly containing resource group name) that I want to create in order to get a "presudo-random" (but stable) name. Attempting to do so from a shell script is annoying.

**Describe the solution you'd like**
It would be of a lot of value to expose the functionality from the `az create` commands - e.g. `az storage account create -g somegroup -n somename --uniqify-name`

**Describe alternatives you've considered**
- Make name optional and default it to a uniqueString equivalent.
- Provide an `az name create --resource-group some group --name someame`

**Additional context**