fix(core): Adds SkipLocalsInitAttribute support, optimizes broadcasted packets (#363)

- [X] Adds support for `SkipLocalsInitAttribute`. SkipLocalsInitAttribute skips initializing stack variables including `stackalloc`. I don't think it is wired/working yet but should be implemented soon.
- [X] Optimizes broadcasted packets by checking if the first byte (packet ID) is non-zero. If it is already set, it reuses the buffer.
- [X] Removes unnecessary refs to Spans. I don't think the Span struct itself is mutable, so a ref is not helpful.

Projects/Server.Tests/Tests/Network/Packets/Outgoing/EffectPacketTests.cs

@@ -50,7 +50,7 @@ namespace Server.Tests.Network
 
             Span<byte> actual = stackalloc byte[OutgoingEffectPackets.ParticleEffectLength];
             OutgoingEffectPackets.CreateParticleEffect(
-                ref actual,
+                actual,
                 effectType, from, to, itemId, fromPoint, toPoint, speed, duration, direction,
                 explode, hue, renderMode, effect, explodeEffect, explodeSound, serial, layer,
                 unknown
@@ -82,7 +82,7 @@ namespace Server.Tests.Network
 
             Span<byte> actual = stackalloc byte[OutgoingEffectPackets.HuedEffectLength];
             OutgoingEffectPackets.CreateHuedEffect(
-                ref actual,
+                actual,
                 effectType, from, to, itemId, fromPoint, toPoint, speed,
                 duration, direction, explode, hue, renderMode
             );
@@ -110,10 +110,7 @@ namespace Server.Tests.Network
             var expected = new BoltEffect(entity, hue).Compile();
 
             Span<byte> actual = stackalloc byte[OutgoingEffectPackets.BoltEffectLength];
-            OutgoingEffectPackets.CreateBoltEffect(
-                ref actual,
-                entity, hue
-            );
+            OutgoingEffectPackets.CreateBoltEffect(actual, entity, hue);
 
             AssertThat.Equal(actual, expected);
         }