Add support for Microsoft Azure

[samkumar]

I successfully spawned Azure instances and ran replication jobs between two Azure instances and between an AWS instance and an Azure instance. To use this, you'll need to set up Azure credentials. The code uses DefaultAzureCredential, which checks for credentials in several different places (see https://docs.microsoft.com/en-us/python/api/azure-identity/azure.identity.defaultazurecredential?view=azure-python). You'll also need to specify your Azure subscription ID as a command line argument.

The code is not optimized, and there is considerable room for optimizing the operations for managing Azure resources. We can discuss making it more efficient if necessary.

[samkumar]

Here's a command you can use to test functionality:

$ skylark replicate-random aws:eu-central-1 azure:westus2 --chunk-size-mb 16 --n-chunks 1 --num-gateways 1 --num-outgoing-connections 1 --azure-subscription <your-azure-subscription-id>

[parasj]

LGTM thanks!