Replace ThreadLocal with ConcurrentHashMap in CommandSourceStack (#6325)

This object is created so often that it likely creates problems with the
ThreadLocalMap because the weak references can't be cleaned up fast
enough. This has manifest as lag seemingly caused by WorldEdit:
https://github.com/EngineHub/WorldEdit/issues/1668

patches/server/0492-Thread-Safe-Vanilla-Command-permission-checking.patch

@@ -9,7 +9,7 @@ to race conditions.
 Plus, .canUse we want to be safe for async anyways.
 
 diff --git a/src/main/java/com/mojang/brigadier/tree/CommandNode.java b/src/main/java/com/mojang/brigadier/tree/CommandNode.java
-index aa3a1795850a419f624f14bd7c4daab0020779d0..39708be1b445791b053023dec16ad7d4efcc9048 100644
+index aa3a1795850a419f624f14bd7c4daab0020779d0..e91d7dd7517c556d12541098878de9be6b0663ba 100644
 --- a/src/main/java/com/mojang/brigadier/tree/CommandNode.java
 +++ b/src/main/java/com/mojang/brigadier/tree/CommandNode.java
 @@ -74,10 +74,10 @@ public abstract class CommandNode<S> implements Comparable<CommandNode<S>> {
@@ -17,34 +17,45 @@ index aa3a1795850a419f624f14bd7c4daab0020779d0..39708be1b445791b053023dec16ad7d4
          if (source instanceof CommandSourceStack) {
              try {
 -                ((CommandSourceStack) source).currentCommand = this;
-+                ((CommandSourceStack) source).currentCommand.set(this); // Paper
++                ((CommandSourceStack) source).currentCommand.put(Thread.currentThread(), this); // Paper
                  return this.requirement.test(source);
              } finally {
 -                ((CommandSourceStack) source).currentCommand = null;
-+                ((CommandSourceStack) source).currentCommand.set(null); // Paper
++                ((CommandSourceStack) source).currentCommand.remove(Thread.currentThread()); // Paper
              }
          }
          // CraftBukkit end
 diff --git a/src/main/java/net/minecraft/commands/CommandSourceStack.java b/src/main/java/net/minecraft/commands/CommandSourceStack.java
-index a59d14e61fcbca7861a5593d0717b81262ccbdc5..134bb2a4826419110c10a483834747b942576e58 100644
+index a59d14e61fcbca7861a5593d0717b81262ccbdc5..71e29d29ed5c2d61832e2f124967bb223708406f 100644
 --- a/src/main/java/net/minecraft/commands/CommandSourceStack.java
 +++ b/src/main/java/net/minecraft/commands/CommandSourceStack.java
-@@ -54,7 +54,7 @@ public class CommandSourceStack implements SharedSuggestionProvider, com.destroy
+@@ -9,8 +9,10 @@ import com.mojang.brigadier.suggestion.Suggestions;
+ import com.mojang.brigadier.suggestion.SuggestionsBuilder;
+ import java.util.Collection;
+ import java.util.Iterator;
++import java.util.Map;
+ import java.util.Set;
+ import java.util.concurrent.CompletableFuture;
++import java.util.concurrent.ConcurrentHashMap;
+ import java.util.function.BinaryOperator;
+ import java.util.stream.Stream;
+ import javax.annotation.Nullable;
+@@ -54,7 +56,7 @@ public class CommandSourceStack implements SharedSuggestionProvider, com.destroy
      private final ResultConsumer<CommandSourceStack> consumer;
      private final EntityAnchorArgument.Anchor anchor;
      private final Vec2 rotation;
 -    public volatile CommandNode currentCommand; // CraftBukkit
-+    public ThreadLocal<CommandNode> currentCommand = new ThreadLocal<>(); // CraftBukkit // Paper
++    public Map<Thread, CommandNode> currentCommand = new ConcurrentHashMap<>(); // CraftBukkit // Paper
  
      public CommandSourceStack(CommandSource output, Vec3 pos, Vec2 rot, ServerLevel world, int level, String name, Component displayName, MinecraftServer server, @Nullable Entity entity) {
          this(output, pos, rot, world, level, name, displayName, server, entity, false, (commandcontext, flag, j) -> {
-@@ -175,9 +175,11 @@ public class CommandSourceStack implements SharedSuggestionProvider, com.destroy
+@@ -175,9 +177,11 @@ public class CommandSourceStack implements SharedSuggestionProvider, com.destroy
      @Override
      public boolean hasPermission(int level) {
          // CraftBukkit start
 -        CommandNode currentCommand = this.currentCommand;
 +        // Paper start - fix concurrency issue
-+        CommandNode currentCommand = this.currentCommand.get();
++        CommandNode currentCommand = this.currentCommand.get(Thread.currentThread());
          if (currentCommand != null) {
              return this.hasPermission(level, org.bukkit.craftbukkit.command.VanillaCommandWrapper.getPermission(currentCommand));
 +            // Paper end