message_edit: Fix unmute of topic when topic name is edited.

Previously, when a topic was edited (including being resolved), it
would become unmuted for any users who had muted it, which was
annoying.

While it's not possible to determine the user's intent completely,
this is clearly incorrect behavior in the `change_all` case, such as
resolving a topic.

The comments discuss some scenarios where we might want to enhance
this further, but this is the best we can do without large increases
in complexity.

Fixes #15210.

Co-authored-by: akshatdalton <akshat.dak@students.iiit.ac.in>

zerver/lib/user_topics.py

@@ -1,6 +1,7 @@
 import datetime
 from typing import Any, Callable, Dict, List, Optional, Tuple
 
+from django.db.models.query import QuerySet
 from django.utils.timezone import now as timezone_now
 from sqlalchemy.sql import ClauseElement, and_, column, not_, or_
 from sqlalchemy.types import Integer
@@ -152,3 +153,13 @@ def build_topic_mute_checker(user_profile: UserProfile) -> Callable[[int, str],
         return (recipient_id, topic.lower()) in tups
 
     return is_muted
+
+
+def get_users_muting_topic(stream_id: int, topic_name: str) -> QuerySet[UserProfile]:
+    return UserProfile.objects.select_related("realm").filter(
+        id__in=UserTopic.objects.filter(
+            stream_id=stream_id,
+            visibility_policy=UserTopic.MUTED,
+            topic_name__iexact=topic_name,
+        ).values("user_profile_id")
+    )