Update and cleanup Celery integration (#2891)

Cleanup the Celery integration to make it easier to work on it and also update to the new minimum supported Celery versions and the new Scopes API.

Author: antonpirker

sentry_sdk/crons/api.py

@@ -1,6 +1,6 @@
 import uuid
 
-from sentry_sdk import Hub
+import sentry_sdk
 from sentry_sdk._types import TYPE_CHECKING
 
 
@@ -17,7 +17,7 @@ def _create_check_in_event(
     monitor_config=None,
 ):
     # type: (Optional[str], Optional[str], Optional[str], Optional[float], Optional[Dict[str, Any]]) -> Event
-    options = Hub.current.client.options if Hub.current.client else {}
+    options = sentry_sdk.get_client().options
     check_in_id = check_in_id or uuid.uuid4().hex  # type: str
 
     check_in = {
@@ -52,7 +52,6 @@ def capture_checkin(
         monitor_config=monitor_config,
     )
 
-    hub = Hub.current
-    hub.capture_event(check_in_event)
+    sentry_sdk.capture_event(check_in_event)
 
     return check_in_event["check_in_id"]