message_send: Fix wildcard_mentioned flag unset for few participants.

For topic wildcard mentions, the 'wildcard_mentioned' flag is set
for those user messages having 'user_profile_id' in
'topic_participant_user_ids', i.e. all topic participants.

Earlier, the flag was set if the 'user_profile_id' exists in
'all_topic_wildcard_mention_user_ids'.
'all_topic_wildcard_mention_user_ids' contains the ids of those
users who are topic participants and have enabled notifications
for '@topic' mentions.

The earlier approach was incorrect, as it would set the
'wildcard_mentioned' flag only for those topic participants
who have enabled the notifications for '@topic' mention instead
of setting the flag for all the topic participants.

The bug was introduced in 4c9d26c.

zerver/lib/message.py

@@ -191,6 +191,8 @@ class SendMessageRequest:
     # (having stream wildcard) is being sent to, and have the
     # 'followed_topic_wildcard_mentions_notify' setting ON.
     stream_wildcard_mention_in_followed_topic_user_ids: Set[int]
+    # A topic participant is anyone who either sent or reacted to messages in the topic.
+    topic_participant_user_ids: Set[int]
     links_for_embed: Set[str]
     widget_content: Optional[Dict[str, Any]]
     submessages: List[Dict[str, Any]] = field(default_factory=list)