Provide tenant DisplayName and DefaultDomain on az account commands or provide a command to fetch tenant information

**Is your feature request related to a problem? Please describe.**
Selecting correct subscription from `az account list` is hard if identical subscription names are used on multiple tenants because:
1. The command does not output tenants' DisplayName and DefaultDomain
2. AZ CLI does not provide a command to list tenants

**Describe the solution you'd like**
`az account list` and `az account show` should display tenants' DisplayName and DefaultDomain.

**Alternative solution**
Add a command that gives the content of the following REST call: `az rest --method GET --uri https://management.azure.com/tenants?api-version=2020-01-01 --output table --query 'value[]'`. Compare with Get-AzTenant PS Cmdlet

The best-case scenario would be implementing both.