ref(transport): add async type annotations to HTTPTransportCore

Add necessary type annotations to the core HttpTransport to accomodate for async transport.

GH-4568

Author: srothh

sentry_sdk/transport.py

@@ -479,6 +479,9 @@ def _make_pool(
         httpcore.SOCKSProxy,
         httpcore.HTTPProxy,
         httpcore.ConnectionPool,
+        httpcore.AsyncSOCKSProxy,
+        httpcore.AsyncHTTPProxy,
+        httpcore.AsyncConnectionPool,
     ]:
         raise NotImplementedError()