Handle more cases/events where topic data in store needs changing

[sm-sayedi]

This is a follow-up to #1499 (PR #1951). In there, we handle most of the cases where the topic data (which will be tracked in store when #1951 is merged) can be changed, including events such as MessageEvent and UpdateMessageEvent. There are some other events that make it necessary to update the topic data (to clear the topics for a certain channel so that the updated topic list is fetched on demand).

These events are as follows:

• ChannelUpdateEvent when event.historyPublicToSubscribers is present (brought up in #1951 comment, thanks @chrisbobbe).
• ChannelDeleteEvent.
• Probably others that should be thought about when picking this up.

Also in #1951, maxId of a topic in store may not represent a message that is still in the topic because of message moves or deletions. We probably want to clear the topics for that channel in those cases so that the updated data is fetched on demand. In that case, we should handle DeleteMessageEvent too. Discussion: #1951 (comment)

When the topic data for a channel is cleared, we should make sure it behaves properly in the UI, for example, in autocomplete and when the topic-list page is opened.