boxes: Generate complete emoji list for autocomplete from aliases too.

This commit expands the state space for emoji autocomplete by including
emoji names from aliases too. According to our new structure of storing
emoji's, we have a single emoji_name (aka canonical_name) for each code
and all other emoji_names carrying the same emoji_code are stored as
aliases of the canonical emoji.

Tests amended.

tests/ui_tools/test_boxes.py

@@ -630,9 +630,9 @@ def test_generic_autocomplete_streams(
             (":jo", 1, ":joy_cat:"),
             (":jok", 0, ":joker:"),
             (":", 0, ":happy:"),
-            (":", 1, ":joker:"),
-            (":", -2, ":smiley:"),
-            (":", -1, ":smirk:"),
+            (":", 1, ":grinning:"),
+            (":", -2, ":smirk:"),
+            (":", -1, ":smug:"),
             (":nomatch", 0, None),
             (":nomatch", -1, None),
             # Complex autocomplete prefixes.

zulipterminal/ui_tools/boxes.py

@@ -592,7 +592,10 @@ def autocomplete_streams(
     def autocomplete_emojis(
         self, text: str, prefix_string: str
     ) -> Tuple[List[str], List[str]]:
-        emoji_list = list(self.model.active_emoji_data.keys())
+        emoji_list = []
+        for emoji_name, emoji_data in self.model.active_emoji_data.items():
+            emoji_list.append(emoji_name)
+            emoji_list.extend(emoji_data["aliases"])
         emojis = [emoji for emoji in emoji_list if match_emoji(emoji, text[1:])]
         emoji_typeahead = format_string(emojis, ":{}:")