Add debug for sync chunk loads

This patch adds a tool to find calls to getChunkAt which would load
chunks, however it must be enabled by setting the startup flag
-Dpaper.debug-sync-loads=true

- To get a debug log for sync loads, the command is
  /paper syncloadinfo
- To clear clear the currently stored sync load info, use
  /paper syncloadinfo clear

paper-server/src/main/java/io/papermc/paper/command/PaperCommand.java

@@ -38,6 +38,7 @@ public final class PaperCommand extends Command {
         commands.put(Set.of("reload"), new ReloadCommand());
         commands.put(Set.of("version"), new VersionCommand());
         commands.put(Set.of("dumpplugins"), new DumpPluginsCommand());
+        commands.put(Set.of("syncloadinfo"), new SyncLoadInfoCommand());
 
         return commands.entrySet().stream()
             .flatMap(entry -> entry.getKey().stream().map(s -> Map.entry(s, entry.getValue())))