Migrate to Zarr 3

Pre-work to #6

This MR has the following:

1. Migration to Zarr 3 API while removing the deprecated yet still supported Zarr 2 API usage.
2. Essential fixes for the main-branch resulting from the learnings out of the global-hackathon exploits (The non-essential ones will be fixed in a seperate branch).

apps/hiopy/worker.py

 #!/usr/bin/env python3
 
-import json
-import logging
-from argparse import ArgumentParser
-from itertools import chain, groupby
-
-import numpy as np
-import zarr
-from coyote import (
-    Coyote,
-    ensure_enddef,
-    get_field_metadata,
-    group_comm_rank,
-    group_comm_size,
-    init,
-    run,
-    start_datetime,
-)
-
+from coyote import Coyote, group_comm_rank, group_comm_size, init, run, start_datetime
 from ._data_handler import DataHandler
 from ._distribute_work import distribute_work
 from ._grids import def_grid, grid_id
 from ._zarr_utils import get_time_axis, get_var_group
 from .loco import LocoServer
 
+import numpy as np
+import zarr
+import logging
+from argparse import ArgumentParser
+from itertools import chain, groupby
+
+
 
 def main():
     parser = ArgumentParser()