Due to differences between the codepoints of flag emojis in
`emoji_map.json` and iamcal's dataset, we need to patch the
css classes for the flag emojis temporarily until the migration
to iamcal's dataset is complete inorder to render them properly.
There is a difference between the images of flag emojis in our
old emoji farm and iamcal's spritesheets and since we have not
yet switched to using spritesheets for displaying emojis in
messages, there is a difference between the flag emojis as
rendered in messages and in emoji pickers.
This is a follow-up to merging the compose and reactions emoji
pickers. The logic for what happens when the user picks an emoji via
the hotkeys (i.e. hits `enter`) was still attempting to add a reaction
to the currently selected message unconditionally.
This commit adds a check in the two `enter` key code paths, and does
the correct thing in each case.
Fixes#4736.
This removes the old compose emoji picker in its entirety, changing
the few callbacks needed to launch the reactions-style emoji picker
instead and hook it up properly.
Callbacks for reactions and composing messages are distinguished by
selecting for, respectively, the .reaction and .composition classes.
Fixes#4122.