Return to message list upon "Mark as unread"

[gitstart]

fixes #7081

PR Description

This PR returns to this of messages(or go to the next message depending on the settings) when a message is marked as unread,

Issue video

https://www.loom.com/share/9093c59a60e840218aee631b8a10da20

Demo video

https://www.loom.com/share/4740c3e1de434a57b92be13c37352d4d

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This code was written and reviewed by GitStart Community. Growing great engineers, one PR at a time.

[cketti]

Thank you for your pull request 👍 Apologies, for not providing feedback earlier.

We postponed dealing with this pull request because its existence highlights a couple of organizational issues we have as an open source project. We're now (slowly) beginning to address those.

Initially we weren't sure if we even wanted to add this feature. Since then we've talked about this internally and decided that yes, we're fine with adding an option that controls what happens when a message is marked as unread from the message view. Please see this comment for more information.

For the implementation, please discard the existing changes and do the following:

1. Add a new setting "Return to list after mark as unread". See 0cad7f3 for an example of what changes are necessary to add a new setting. (Change K9, Settings, GeneralSettingsDescription, GeneralSettingsDataStore, general_settings.xml, and strings.xml)
2. Add a new method to MessageViewFragmentListener to handle the navigation after a "mark as unread" operation, e.g. performNavigationAfterMarkAsUnread().
3. Call this method after marking a message as unread (and only when marking as unread; not when marking as read!)
4. Implement the navigation logic in MessageList (i.e. call returnToMessageList() when necessary).

It has been quite a while since you've started work on this. If you have since moved on and don't want to implement these changes, that's totally understandable. In that case please add a quick comment to let us know and we'll work on this ourselves.

Again, apologies for sitting on this for so long and not making this a smoother experience for you as a contributor. We'll try to do better in the future.

[cketti]

Since there hasn't been any activity for more than a month, I considered this pull request abandoned and implemented the change myself. See #7350.