fix(core): Converts boat packets (#416)

- [X] Converts boat packets
- [X] Makes a packet container builder for packet 0xF7
- [X] Generalizes world item packet so it works for mobiles too

Notes:
- This PR doesn't address proper smooth movement for boats.

Projects/UOContent/Items/Misc/LOSBlocker.cs

@@ -38,13 +38,13 @@ namespace Server.Items
         private void SendGMItem(NetState ns)
         {
             // GM Packet
-            Span<byte> buffer = stackalloc byte[OutgoingItemPackets.MaxWorldItemPacketLength];
+            Span<byte> buffer = stackalloc byte[OutgoingEntityPackets.MaxWorldEntityPacketLength];
 
             int length;
 
             if (ns.StygianAbyss)
             {
-                length = OutgoingItemPackets.CreateWorldItemNew(buffer, this, ns.HighSeas);
+                length = OutgoingEntityPackets.CreateWorldEntity(buffer, this, ns.StygianAbyss, ns.HighSeas);
                 BinaryPrimitives.WriteUInt16BigEndian(buffer.Slice(8, 2), GMItemId);
             }
             else