[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

cameraserver/multiCameraServer/src/main/java/edu/wpi/Main.java

@@ -176,7 +176,7 @@ public final class Main {
     } else {
       System.out.println("Setting up NetworkTables client for team " + team);
       ntinst.setServerTeam(team);
-      ntinst.startClient4();
+      ntinst.startClient4("multicameraserver");
     }
 
     // start cameras