fix(core): Fixes OPL packets (#395)

- [X] Fixes an issue with OPL packets using the wrong endianness and not updating the position properly.
- [X] Fixes an issue with SpanWriter not updating bytes written when it is used adhoc.
- [X] Moves packet creation for OPL inside the SendInfoTo function.

Bumps release version

Projects/Server/Network/Packets/IncomingEntityPackets.cs

@@ -13,6 +13,8 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>. *
  *************************************************************************/
 
+using System;
+
 namespace Server.Network
 {
     public static class IncomingEntityPackets