Currently, the emoji_status set by the user is only seen in the buddy
list, it would be useful to show the emoji_status in other places as
well.
As such this commit does the prep work of decoupling the
selected_emoji style in user_status.css from the .status_emoji
style... by having it always override the value of "top".
In this commit, we update the UI to:
* Display emoji on the buddy list (right side sidebar).
* Display the emoji picker on the set status overlay.
It also updates the `z-index` of
`#set_user_status_modal`, which was changed from 105
to 1050 in 166bfa4cf8. We change it back to 105, so
emoji-popover can be visible on top of the
`#set_user_status_modal`.
We also remove the `tabindex` property from the
`#set_user_status_modal` so it can allow keyboard
events for emoji popover.