[ntcore] Various NT4 fixes (#4474)

* TopicListener: Fix Add() return values
* Update PubSubOption poll storage documentation
* Update NetworkTableEntry::GetValue() doc
* Add documentation regarding asynchronous callbacks
* Unpublish entry: set publisher to nullptr
* Implement ValueListenerPoller default constructor
* Remove SetNetworkIdentity, make parameter to StartClient
* URI-escape client ID, improve error message
* Add connected message with client id; also improve disconnected message a bit
* Handle SetServers either before or after StartClient
* Fix client use-after-free; also delay reconnect after disconnect to rate limit
* Don't re-announce to already subscribed client; we especially don't want to send the last value again
* Always accept in-order sets, only use timestamp for tiebreak
* Fix LocalStorage::StartNetwork race
* Remove unused/unimplemented function

Also:
* [glass] Remove debug print
* [glass] Fix mpack string decoding
* [cameraserver] Fix up startclient

glass/src/libnt/native/cpp/NetworkTables.cpp

@@ -176,7 +176,6 @@ static void UpdateMsgpackValueSource(NetworkTablesModel::ValueSource* out,
     case mpack::mpack_type_str: {
       std::string str;
       mpack_read_str(&r, &tag, &str);
-      mpack_done_str(&r);
       out->UpdateFromValue(nt::Value::MakeString(std::move(str), time), name,
                            "");
       break;
@@ -461,7 +460,6 @@ void NetworkTablesModel::Update() {
                              entry->info.type_str);
       if (wpi::starts_with(entry->info.name, '$') && entry->value.IsRaw() &&
           entry->info.type_str == "msgpack") {
-        fmt::print(stderr, "Updating meta-topic {}\n", entry->info.name);
         // meta topic handling
         if (entry->info.name == "$clients") {
           UpdateClients(entry->value.GetRaw());