Cleanup to the /player command (#1690)

* Small cleanup to `/player` command

There should be no changes to users

* Use extracted `source` variable

* Inline another single-use small function

* Inline another trivial helper

* Import inner classes of the ActionPack

* Rename `literalargumentbuilder` variable

* Compact unnecessary three lines into one

* Inline `source.getServer` and pass `Vec3` to `createFake`

This gets outside of "just" the command, but it's fine

* Unpick name length constant

* Pass `Vec3` directly to `BlockPos.containing`

src/main/java/carpet/patches/EntityPlayerMPFake.java

@@ -26,6 +26,7 @@ import net.minecraft.world.level.GameType;
 import net.minecraft.world.level.Level;
 import net.minecraft.world.level.block.entity.SkullBlockEntity;
 import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.phys.Vec3;
 import carpet.fakes.ServerPlayerInterface;
 import carpet.utils.Messenger;
 
@@ -37,7 +38,7 @@ public class EntityPlayerMPFake extends ServerPlayer
     public Runnable fixStartingPosition = () -> {};
     public boolean isAShadow;
 
-    public static EntityPlayerMPFake createFake(String username, MinecraftServer server, double d0, double d1, double d2, double yaw, double pitch, ResourceKey<Level> dimensionId, GameType gamemode, boolean flying)
+    public static EntityPlayerMPFake createFake(String username, MinecraftServer server, Vec3 pos, double yaw, double pitch, ResourceKey<Level> dimensionId, GameType gamemode, boolean flying)
     {
         //prolly half of that crap is not necessary, but it works
         ServerLevel worldIn = server.getLevel(dimensionId);
@@ -65,9 +66,9 @@ public class EntityPlayerMPFake extends ServerPlayer
             gameprofile = result.get();
         }
         EntityPlayerMPFake instance = new EntityPlayerMPFake(server, worldIn, gameprofile, false);
-        instance.fixStartingPosition = () -> instance.moveTo(d0, d1, d2, (float) yaw, (float) pitch);
+        instance.fixStartingPosition = () -> instance.moveTo(pos.x, pos.y, pos.z, (float) yaw, (float) pitch);
         server.getPlayerList().placeNewPlayer(new FakeClientConnection(PacketFlow.SERVERBOUND), instance);
-        instance.teleportTo(worldIn, d0, d1, d2, (float)yaw, (float)pitch);
+        instance.teleportTo(worldIn, pos.x, pos.y, pos.z, (float) yaw, (float) pitch);
         instance.setHealth(20.0F);
         instance.unsetRemoved();
         instance.setMaxUpStep(0.6F);