action sheet: Add "Move message(s)" button to message action sheet

[chrisbobbe]

zulip-mobile issue: zulip/zulip-mobile#5165

We should make it possible to move some messages in a topic by adding a "Move message(s)" option to the message action sheet. Selecting this option should open a modal with options like in the web app:

Related issues

• action sheet: Add "Move topic" button to topic action sheet #1439

[chrisbobbe]

This was requested in beta feedback to support@:

Also, just like the old mobile app, there is no "move message" feature. This isn't a game breaker, since I can log into the web version of my chat to handle these administrative tasks.

[chrisbobbe]

We've had feedback that this feature would be helpful for moderator/admin users who often need to move messages (their own and others'): zulip/zulip-mobile#5165 (comment)