Added some love for sovereign clouds (#536)
Added some love for sovereign clouds (#536)

* Added some love for sovereign clouds
- Added consts for their base URLs
- Added funcs to create clients as easy as it is for the public cloud

* No longer duplicating methods

Azure/azure-sdk-for-go,marstr/azure-sdk-for-go,Azure/azure-sdk-for-go,marstr/azure-sdk-for-go,curoverse/azure-sdk-for-go,curoverse/azure-sdk-for-go,marstr/azure-sdk-for-go,Azure/azure-sdk-for-go,Azure/azure-sdk-for-go,colemickens/azure-sdk-for-go