Split delete modal trigger for reuse (#5740)

Spllit delete modal trigger for reuse and make emoji delete
to use this modal trigger.

webapp/i18n/en.json

@@ -1275,6 +1275,9 @@
   "emoji_list.add": "Add Custom Emoji",
   "emoji_list.creator": "Creator",
   "emoji_list.delete": "Delete",
+  "emoji_list.delete.confirm.button": "Delete",
+  "emoji_list.delete.confirm.msg": "This action permanently deletes the custom emoji. Are you sure you want to delete it?",
+  "emoji_list.delete.confirm.title": "Delete Custom Emoji",
   "emoji_list.empty": "No Custom Emoji Found",
   "emoji_list.header": "Custom Emoji",
   "emoji_list.help": "Custom emoji are available to everyone on your server. Type ':' in a message box to bring up the emoji selection menu. Other users may need to refresh the page before new emojis appear.",