streams: Refactor code to set group-based stream settings.

We add stream_permission_group_settings object which is
similar to property_types framework used for realm settings.

This commit also adds GroupPermissionSetting dataclass for
defining settings inside stream_permission_group_settings.

We add "do_change_stream_group_based_setting" function which
is called in loop to update all the group-based stream settings
and it is now used to update 'can_remove_subscribers_group'
setting instead of "do_change_can_remove_subscribers_group".

We also change the variable name for event_type field of
RealmAuditLog objects to STREAM_GROUP_BASED_SETTING_CHANGED
since this will be used for all group-based stream settings.

'property' field is also added to extra_data field to identify
the setting for which RealmAuditLog object was created.

We will add a migration in further commits which will add the
property field to existing RealmAuditLog objects created for
changing can_remove_subscribers_group setting.

zerver/lib/types.py

@@ -272,3 +272,10 @@ class RealmPlaygroundDict(TypedDict):
     name: str
     pygments_language: str
     url_prefix: str
+
+
+@dataclass
+class GroupPermissionSetting:
+    require_system_group: bool
+    allow_internet_group: bool
+    allow_owners_group: bool