test: Include eg.selfUser by default in eg.initialSnapshot

Over the next few commits, we'll ensure that all tests' data put the
self-user in the users list of the initial snapshot.  This will help
by making that happen automatically for the majority of tests.

Author: gnprice

test/example_data.dart

@@ -1276,7 +1276,7 @@ InitialSnapshot initialSnapshot({
     serverEmojiDataUrl: serverEmojiDataUrl
       ?? realmUrl.replace(path: '/static/emoji.json'),
     realmEmptyTopicDisplayName: realmEmptyTopicDisplayName ?? defaultRealmEmptyTopicDisplayName,
-    realmUsers: realmUsers ?? [],
+    realmUsers: realmUsers ?? [selfUser],
     realmNonActiveUsers: realmNonActiveUsers ?? [],
     crossRealmBots: crossRealmBots ?? [],
   );

test/model/autocomplete_test.dart

@@ -446,8 +446,8 @@ void main() {
       List<Message> messages = const [],
     }) async {
       store = eg.store(initialSnapshot: eg.initialSnapshot(
+        realmUsers: users,
         recentPrivateConversations: dmConversations));
-      await store.addUsers(users);
       await store.addUserGroups(userGroups);
       await store.addMessages(messages);
     }

test/widgets/new_dm_sheet_test.dart

@@ -34,9 +34,10 @@ Future<void> setupSheet(WidgetTester tester, {
   final testNavObserver = TestNavigatorObserver()
     ..onPushed = (route, _) => lastPushedRoute = route;
 
-  await testBinding.globalStore.add(eg.selfAccount, eg.initialSnapshot());
+  await testBinding.globalStore.add(eg.selfAccount, eg.initialSnapshot(
+    realmUsers: users,
+  ));
   store = await testBinding.globalStore.perAccount(eg.selfAccount.id);
-  await store.addUsers(users);
   if (mutedUserIds != null) {
     await store.setMutedUsers(mutedUserIds);
   }