core, tests, ui: keep member order with role index, skip down-migration schema comparison, reload support list on return with older remote hosts

apps/ios/Shared/Model/SimpleXAPI.swift

@@ -592,10 +592,8 @@ private func processSendMessageCmd(toChatType: ChatType, cmd: ChatCommand) async
     } else {
         r = await chatApiSendCmd(cmd, bgDelay: msgDelay)
         if case let .result(.newChatItems(_, aChatItems)) = r {
-            await MainActor.run {
-                for aChatItem in aChatItems {
-                    chatModel.upsertSupportChatMember(aChatItem.chatInfo)
-                }
+            if let last = aChatItems.last {
+                await MainActor.run { chatModel.upsertSupportChatMember(last.chatInfo) }
             }
             return aChatItems.map { $0.chatItem }
         }
@@ -2062,10 +2060,10 @@ func apiLeaveGroup(_ groupId: Int64) async throws -> GroupInfo {
 }
 
 // use ChatModel's loadGroupMembers from views
-func apiListMembers(_ groupId: Int64) async -> [GroupMember]? {
+func apiListMembers(_ groupId: Int64) async -> [GroupMember] {
     let r: APIResult<ChatResponse2> = await chatApiSendCmd(.apiListMembers(groupId: groupId))
     if case let .result(.groupMembers(_, group)) = r { return group.members }
-    return nil
+    return []
 }
 
 func filterMembersToAdd(_ ms: [GMember]) -> [Contact] {