feat: added azure vm start stop support

[zeteoh]

This pr adds azure start/stop support when users indicate an azure flag
river-guide --provider azure

Fixes #53.

To test, run to create VMs in azure:

az vm create \
  --resource-group FRGAPAC \                 
  --name testtwo \
  --image Ubuntu2204 \
  --admin-username azureuser \
  --generate-ssh-keys \
  --location southeastasia

Assumption:

1. User have local az configs

Default:

1. Subscription ID in local az config points to the desired resource block
2. Resource block name is FRGAPAC

Alternatively:
Users can specify the resource block name or subscription id, for example:

./river-guide --provider azure --resource-block-name FRGAPAC
./river-guide --provider azure --resource-block-name FRGAPAC --subscription-id <id>