Add 'SyncedCoreInfo' to Extended Features list, clean up

In ExtendedFeature.kt, Quasseldroid should add support for SyncedCoreInfo, and (if ready) remove LongMessageTime.

SyncedCoreInfo is an informational flag to let the client know the core will send signals to update the CoreInfo object. The desktop client uses this to detect when a legacy core won't refresh information, and applies the resynchronization behavior of past stable releases instead. The original pull request on Quassel offers more information.

Quasseldroid never supported non-synced CoreInfo data of Connected clients, so there shouldn't be any code changes beyond adding the feature flag to tell the core that this feature is (already) supported.

Removing LongMessageTime is just cleaning up informational messages near a potential 0.13 beta. If personal cores aren't yet ready, feel free to hold off.

Patch

--- <unnamed>
+++ <unnamed>
@@ -47,15 +47,16 @@
   RemoteDisconnect,
   /** Transmit features as list of strings */
   ExtendedFeatures,
-  /** Serialize message time as 64-bit */
+  /** Serialize time as 64-bit */
   LongTime,
-  LongMessageTime,
   /** Real Name and Avatar URL in backlog */
   RichMessages,
   /** Backlogmanager supports filtering backlog by messagetype */
   BacklogFilterType,
   /** 64-bit IDs for messages */
-  LongMessageId;
+  LongMessageId,
+  /** CoreInfo dynamically updated using signals */
+  SyncedCoreInfo;
 
   companion object {
     private val map = values().associateBy(ExtendedFeature::name)

---

I'd file a pull request, but alas, GitLab is not letting me fork the project due to hitting the project limit of 0.