user_topics: Refactor add_topic_mute.

In order to support different types of topic visibility policies,
this renames 'add_topic_mute' to
'set_user_topic_visibility_policy_in_database'
and refactors it to accept a parameter 'visibility_policy'.

Create a corresponding UserTopic row for any visibility policy,
not just muting topics.

When a UserTopic row for (user_profile, stream, topic, recipient_id)
exists already, it updates the row with the new visibility_policy.

In the event of a duplicate request, raises a JsonableError.
i.e., new_visibility_policy == existing_visibility_policy.

There is an increase in the database query count in the message-edit
code path.

Reason:
Earlier, 'add_topic_mute' used 'bulk_create' which either
creates or raises IntegrityError -- 1 query.

Now, 'set_user_topic_visibility_policy' uses get_or_create
-- 2 queries in the case of creating new row.

We can't use the previous approach, because now we have to
handle the case of updating the visibility_policy too.
Also, using bulk_* for a single row is not the correct way.

Co-authored-by: Kartik Srivastava <kaushiksri0908@gmail.com>
Co-authored-by: Prakhar Pratyush <prakhar841301@gmail.com>

zerver/views/user_topics.py

@@ -1,13 +1,11 @@
 import datetime
 from typing import Optional
 
-from django.db import IntegrityError
 from django.http import HttpRequest, HttpResponse
 from django.utils.timezone import now as timezone_now
 from django.utils.translation import gettext as _
 
 from zerver.actions.user_topics import do_set_user_topic_visibility_policy
-from zerver.lib.exceptions import JsonableError
 from zerver.lib.request import REQ, has_request_variables
 from zerver.lib.response import json_success
 from zerver.lib.streams import (
@@ -34,16 +32,13 @@ def mute_topic(
         assert stream_id is not None
         (stream, sub) = access_stream_by_id(user_profile, stream_id)
 
-    try:
-        do_set_user_topic_visibility_policy(
-            user_profile,
-            stream,
-            topic_name,
-            visibility_policy=UserTopic.MUTED,
-            last_updated=date_muted,
-        )
-    except IntegrityError:
-        raise JsonableError(_("Topic already muted"))
+    do_set_user_topic_visibility_policy(
+        user_profile,
+        stream,
+        topic_name,
+        visibility_policy=UserTopic.MUTED,
+        last_updated=date_muted,
+    )
 
 
 def unmute_topic(