[UX] Add 3 dots button for gmail thread message

[Kharchevskyi]

or add similar 3 dots button which will show popup with options to choose option(mark as unread, delete message, archive) for selected message. And buttons on top will acts on whole threads

Originally posted by @Kharchevskyi in #608 (comment)

[tomholub]

closing as a dupplicate the top icons that act on whole thread are already present, three dots will be added in PR #1066 and Gmail app doesn't have a way to modify individual messages anyway.

[tomholub]

There's still three dots that act on whole thread (in Gmail app) but we don't need any of that functionality yet.