[Performance] Refactor Azure SDK usage (skypilot-org#4139)

* [Performance] Refactor Azure SDK usage

* lazy import and address comments

* address comments

sky/adaptors/azure.py

@@ -69,6 +69,17 @@ def exceptions():
     return azure_exceptions
 
 
+@functools.lru_cache()
+@common.load_lazy_modules(modules=_LAZY_MODULES)
+def azure_mgmt_models(name: str):
+    if name == 'compute':
+        from azure.mgmt.compute import models
+        return models
+    elif name == 'network':
+        from azure.mgmt.network import models
+        return models
+
+
 # We should keep the order of the decorators having 'lru_cache' followed
 # by 'load_lazy_modules' as we need to make sure a caller can call
 # 'get_client.cache_clear', which is a function provided by 'lru_cache'

sky/provision/azure/config.py

@@ -46,6 +46,7 @@ def bootstrap_instances(
         region: str, cluster_name_on_cloud: str,
         config: common.ProvisionConfig) -> common.ProvisionConfig:
     """See sky/provision/__init__.py"""
+    # TODO: use new azure sdk instead of ARM deployment.
     del region  # unused
     provider_config = config.provider_config
     subscription_id = provider_config.get('subscription_id')