emojis: Use get_emoji_data.

The previous function was poorly named, asked for a
Realm object when realm_id sufficed, and returned a
tuple of strings that had different semantics.

I also avoid calling it duplicate times in a couple
places, although it was probably rarely the case that
both invocations actually happened if upstream
validations were working.

Note that there is a TypedDict called EmojiInfo, so I
chose EmojiData here.  Perhaps a better name would be
TinyEmojiData or something.

I also simplify the reaction tests with a verify
helper.

zerver/views/reactions.py

@@ -5,7 +5,7 @@ from django.http import HttpRequest, HttpResponse
 from django.utils.translation import gettext as _
 
 from zerver.actions.reactions import check_add_reaction, do_remove_reaction
-from zerver.lib.emoji import emoji_name_to_emoji_code
+from zerver.lib.emoji import get_emoji_data
 from zerver.lib.exceptions import JsonableError
 from zerver.lib.message import access_message
 from zerver.lib.request import REQ, has_request_variables
@@ -57,7 +57,7 @@ def remove_reaction(
         # without needing the mapping between emoji names and codes,
         # we allow instead passing the emoji_name and looking up the
         # corresponding code using the current data.
-        emoji_code = emoji_name_to_emoji_code(message.sender.realm, emoji_name)[0]
+        emoji_code = get_emoji_data(message.sender.realm_id, emoji_name).emoji_code
 
     if not Reaction.objects.filter(
         user_profile=user_profile,