Add comprehensive suggestions to many commands.

All patterns now have suggestions, including recursive patterns.
Suggestions will suggest blocks and block states.
All masks now have suggestions, though mask intersections are not
yet supported due to issues with quotes strings.
EntityRemover and ItemFactory now also have completions, as well
as all RegistryConverters (though I am unsure how many are actually
used).

Also use paper's AsyncTabComplete event, if available.

worldedit-bukkit/src/main/java/com/sk89q/worldedit/bukkit/BukkitAdapter.java

@@ -151,7 +151,7 @@ public class BukkitAdapter {
             if (match != null) {
                 return match;
             } else {
-                throw new IllegalArgumentException("Can't find a Bukkit world for " + world);
+                throw new IllegalArgumentException("Can't find a Bukkit world for " + world.getName());
             }
         }
     }