Remove actor handle IDs (#5889)

* Remove actor handle ID from main ActorHandle constructor

* Set the actor caller ID when calling submit task instead of in the actor handle

* Remove ActorHandle::Fork, remove actor handle ID from protobuf

* Make inner actor handle const, remove new_actor_handles

* Move caller ID into the common task spec, start refactoring raylet

* Some fixes for forking actor handles

* Store ActorHandle state in CoreWorker, only expose actor ID to Python

* Remove some unused fields

* lint

* doc

* fix merge

* Remove ActorHandleID from python/cpp

* doc

* Fix core worker test

* Move actor table subscription to CoreWorker, reset actor handles on actor failure

* lint

* Remove GCS client from direct actor

* fix tests

* Fix

* Fix tests for raylet codepath

* Fix local mode

* Fix multithreaded test

* Fix AsyncSubscribe issue...

* doc

* fix serve

* Revert bazel

python/ray/__init__.py

@@ -65,7 +65,6 @@ except ImportError as e:
 from ray._raylet import (
     ActorCheckpointID,
     ActorClassID,
-    ActorHandleID,
     ActorID,
     ClientID,
     Config as _Config,
@@ -154,7 +153,6 @@ __all__ = [
 __all__ += [
     "ActorCheckpointID",
     "ActorClassID",
-    "ActorHandleID",
     "ActorID",
     "ClientID",
     "JobID",