Rework async chunk api implementation

Firstly, the old methods all routed to the CompletableFuture method.
However, the CF method could not guarantee that if the caller
was off-main that the future would be "completed" on-main. Since
the callback methods used the CF one, this meant that the callback
methods did not guarantee that the callbacks were to be called on
the main thread.

Now, all methods route to getChunkAtAsync(x, z, gen, urgent, cb)
so that the methods with the callback are guaranteed to invoke
the callback on the main thread. The CF behavior remains unchanged;
it may still appear to complete on main if invoked off-main.

Secondly, remove the scheduleOnMain invocation in the async
chunk completion. This unnecessarily delays the callback
by 1 tick.

Thirdly, add getChunksAtAsync(minX, minZ, maxX, maxZ, ...) which
will load chunks within an area. This method is provided as a helper
as keeping all chunks loaded within an area can be complicated to
implement for plugins (due to the lacking ticket API), and is
already implemented internally anyways.

Fourthly, remove the ticket addition that occured with getChunkAt
and getChunkAtAsync. The ticket addition may delay the unloading
of the chunk unnecessarily. It also fixes a very rare timing bug
where the future/callback would be completed after the chunk
unloads.

patches/server/0772-Add-Sneaking-API-for-Entities.patch

@@ -1,29 +0,0 @@
-From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
-From: dawon <dawon@dawon.eu>
-Date: Wed, 19 Oct 2022 23:31:53 +0200
-Subject: [PATCH] Add Sneaking API for Entities
-
-
-diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
-index fc48a1de886d48da4cb384472f48cdba974034dd..ca9cda9059a5c1dae1ca9ec09248768274d4e207 100644
---- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
-+++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
-@@ -870,6 +870,18 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
-         return Pose.values()[this.getHandle().getPose().ordinal()];
-     }
- 
-+    // Paper start
-+    @Override
-+    public void setSneaking(boolean sneak) {
-+        this.getHandle().setShiftKeyDown(sneak);
-+    }
-+
-+    @Override
-+    public boolean isSneaking() {
-+        return this.getHandle().isShiftKeyDown();
-+    }
-+    // Paper end
-+
-     @Override
-     public SpawnCategory getSpawnCategory() {
-         return CraftSpawnCategory.toBukkit(this.getHandle().getType().getCategory());