audit_log: Log RealmAuditLog in do_set_realm_property.

Log RealmAuditLog in do_set_realm_property and do_remove_realm_domain.
Tests for the changes are written in test_events because it will save
duplicate code for test_change_realm_property.

docs/tutorials/new-feature-tutorial.md

@@ -293,9 +293,10 @@ active users in a realm.
 
     # zerver/lib/actions.py
 
-    def do_set_realm_property(realm: Realm, name: str, value: bool) -> None:
-      """Takes in a realm object, the name of an attribute to update, and the
-      value to update.
+    def do_set_realm_property(realm: Realm, name: str, value: bool,
+                              acting_user: Optional[UserProfile]=None) -> None:
+      """Takes in a realm object, the name of an attribute to update, the
+         value to update and and the user who initiated the update.
       """
       property_type = Realm.property_types[name]
       assert isinstance(value, property_type), (

docs/tutorials/writing-views.md

@@ -266,7 +266,7 @@ def update_realm(
 ):
     realm = user_profile.realm
     # ...
-            do_set_realm_property(realm, k, v)
+            do_set_realm_property(realm, k, v, acting_user=user_profile)
     # ...
 ```