Support better management of names of archived channels

In https://github.com/zulip/zulip/issues/26661, we plan to rework how archived streams/channels are handled. As part of making these changes, the mobile app should ideally match the web app in how messages in archived channels are displayed.

Implementation

API modeling

• Start passing the new feature level 315 client capability (archived_channels) to get metadata on archived channels.
• Handle stream/update events to live update when channels are archived.

General UI

Most existing functionality should filter out archived channels:

• Inbox page
• Channels pages
• Message lists/feeds
• Look for any other relevant areas, and decide how to handle those

Viewing archived channels and their messages

• When viewing messages in an archived channel (e.g., in search results), append " (archived)" to the end of the channel name. This should be marked for translation. (We can also consider using a different font or a pill in the header bar to indicate archived channels, but just "(archived)" should be fine to start with.)
• The channel icon for an archived channel should be an "archive" icon, rather than "hash_sign" or "lock" etc. See #1992.
• Topic links for archived channels should work. Currently, the server doesn't send data on archived channels to clients. See related discussion here.

Unreads

• When an archived channel is excluded from a given UI (in particular the inbox page), any unreads in the channel should also be excluded from any total numbers of unreads. (Cf #issues > untraceable unread @ 💬 for web.)

References

• Web app / server issue: https://github.com/zulip/zulip/issues/26661