Optimize the config saving, by using "Bulk Saving" method instead.

[AALUND13]

Summary

This change disables the config SaveOnConfigSet during Unbound initialization, and performs a single save after Unbound is fully loaded.

Implementation

• Set config.SaveOnConfigSet = false at startup to prevent per-bind saves.
• After Unbound is fully loaded, schedule a one second save

  this.ExecuteAfterSeconds(1, () =>
  {
      config.Save();
      config.SaveOnConfigSet = true;
  });

Performance Impact

Tested with a 117 mods modpack (019c86b6-941f-216a-a5c1-8ed4ceb102c4).

• Baseline: 99,388 ms average startup time
• With change: 46,563 ms average startup time
• ~50% reduction in startup time (≈2.1× faster)