[Feature-Request] Support customized Azure Environment in AzureCliCredential

[Flanker32]

Description

AzureCliCredential only support regions defined in AzureEnvironment, for user defined environment, environment() will return null and cause NullPointException, refers here

Reproduce

• Register Azure Environment with az cloud register
• Switch Azure Environment with az cloud set -n
• Execute below codes

  final Azure azure = Azure.configure().authenticate(AzureCliCredentials.create()).withDefaultSubscription();
  azure.subscriptions().list().forEach(subs -> System.out.println(subs.subscriptionId()));