Deprecate bukkit scheduler

Every method on that should basically throw, so the API should
reflect that

patches/api/0006-fixup-Region-scheduler-API.patch

@@ -0,0 +1,26 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Spottedleaf <Spottedleaf@users.noreply.github.com>
+Date: Sat, 25 Mar 2023 16:27:40 -0700
+Subject: [PATCH] fixup! Region scheduler API
+
+
+diff --git a/src/main/java/org/bukkit/scheduler/BukkitScheduler.java b/src/main/java/org/bukkit/scheduler/BukkitScheduler.java
+index d2ab2ee1e1e8fbaac4edef5b3ee313ee4ceb6991..8476504e3d54721c64f02eddd5b48193ac8f366b 100644
+--- a/src/main/java/org/bukkit/scheduler/BukkitScheduler.java
++++ b/src/main/java/org/bukkit/scheduler/BukkitScheduler.java
+@@ -7,6 +7,15 @@ import java.util.function.Consumer;
+ import org.bukkit.plugin.Plugin;
+ import org.jetbrains.annotations.NotNull;
+ 
++// Folia start - add new schedulers
++/**
++ * @deprecated Use one of {@link io.papermc.paper.threadedregions.scheduler.RegionScheduler},
++ *                        {@link io.papermc.paper.threadedregions.scheduler.AsyncScheduler},
++ *                        {@link io.papermc.paper.threadedregions.scheduler.EntityScheduler},
++ *                        or {@link io.papermc.paper.threadedregions.scheduler.GlobalRegionScheduler}
++ */
++// Folia end - add new schedulers
++@Deprecated
+ public interface BukkitScheduler {
+ 
+     /**