stream: Add do_change_can_remove_subscribers_group and field to objects.

This commit adds do_change_can_remove_subscriber_group function for
changing can_remove_subscribers_group field of a stream. We also add
can_remove_subscribers_group_id field to stream and subscription
objects.

This function will be helpful for writing tests in next commit.
We would add API and UI support to change this setting in further
commits.

zerver/lib/types.py

@@ -177,6 +177,7 @@ class RawStreamDict(TypedDict):
     are needed to encode the stream for the API.
     """
 
+    can_remove_subscribers_group_id: int
     date_created: datetime.datetime
     description: str
     email_token: str
@@ -216,6 +217,7 @@ class SubscriptionStreamDict(TypedDict):
     """
 
     audible_notifications: Optional[bool]
+    can_remove_subscribers_group_id: int
     color: str
     date_created: int
     description: str
@@ -242,6 +244,7 @@ class SubscriptionStreamDict(TypedDict):
 
 
 class NeverSubscribedStreamDict(TypedDict):
+    can_remove_subscribers_group_id: int
     date_created: int
     description: str
     first_message_id: Optional[int]
@@ -264,6 +267,7 @@ class APIStreamDict(TypedDict):
     with few exceptions and possible additional fields.
     """
 
+    can_remove_subscribers_group_id: int
     date_created: int
     description: str
     first_message_id: Optional[int]