Ocarina of Time: reduce memory use by 64 MiB for each OoT world past the first

Ocarina of Time: limit parallel output to 2, to not waste memory that doesn't benefit speed
Ocarina of Time: remove swarm of os.chdir()

Generate.py

@@ -19,7 +19,7 @@ from worlds.alttp.EntranceRandomizer import parse_arguments
 from Main import main as ERmain
 from Main import get_seed, seeddigits
 import Options
-from worlds.alttp.Items import item_name_groups, item_table
+from worlds.alttp.Items import item_table
 from worlds.alttp import Bosses
 from worlds.alttp.Text import TextTable
 from worlds.alttp.Regions import location_table, key_drop_data
@@ -735,4 +735,4 @@ if __name__ == '__main__':
     confirmation = atexit.register(input, "Press enter to close.")
     main()
     # in case of error-free exit should not need confirmation
-    atexit.unregister(confirmation)
+    atexit.unregister(confirmation)