Don't handle exception in Multiscales init()

[will-moore]

See #258.

This removes the exception handling that was obscuring useful errors there.

E.g. edit a sample zarr to an invalid version, e.g. "version": 0.5 then try to open in napari:

$ napari --plugin napari-ome-zarr /path/to/image.zarr

Traceback (most recent call last):
  File "/Users/wmoore/opt/anaconda3/envs/SSBD/bin/napari", line 8, in <module>
    sys.exit(main())
  File "/Users/wmoore/opt/anaconda3/envs/ssbd/lib/python3.9/site-packages/napari/__main__.py", line 570, in main
    _run()
  File "/Users/wmoore/opt/anaconda3/envs/ssbd/lib/python3.9/site-packages/napari/__main__.py", line 344, in _run
    viewer._window._qt_viewer._qt_open(
  File "/Users/wmoore/opt/anaconda3/envs/ssbd/lib/python3.9/site-packages/napari/_qt/qt_viewer.py", line 867, in _qt_open
    self.viewer.open(
  File "/Users/wmoore/opt/anaconda3/envs/ssbd/lib/python3.9/site-packages/napari/components/viewer_model.py", line 1076, in open
    self._add_layers_with_plugins(
  File "/Users/wmoore/opt/anaconda3/envs/ssbd/lib/python3.9/site-packages/napari/components/viewer_model.py", line 1276, in _add_layers_with_plugins
    layer_data, hookimpl = read_data_with_plugins(
  File "/Users/wmoore/opt/anaconda3/envs/ssbd/lib/python3.9/site-packages/napari/plugins/io.py", line 77, in read_data_with_plugins
    res = _npe2.read(paths, plugin, stack=stack)
  File "/Users/wmoore/opt/anaconda3/envs/ssbd/lib/python3.9/site-packages/napari/plugins/_npe2.py", line 61, in read
    raise e from e
  File "/Users/wmoore/opt/anaconda3/envs/ssbd/lib/python3.9/site-packages/napari/plugins/_npe2.py", line 55, in read
    layer_data, reader = io_utils.read_get_reader(
  File "/Users/wmoore/opt/anaconda3/envs/ssbd/lib/python3.9/site-packages/npe2/io_utils.py", line 66, in read_get_reader
    return _read(
  File "/Users/wmoore/opt/anaconda3/envs/ssbd/lib/python3.9/site-packages/npe2/io_utils.py", line 163, in _read
    ld = read_func(paths, stack=stack)
  File "/Users/wmoore/opt/anaconda3/envs/ssbd/lib/python3.9/site-packages/npe2/manifest/contributions/_readers.py", line 60, in npe1_compat
    return callable_(path)  # type: ignore
  File "/Users/wmoore/Desktop/ZARR/napari-ome-zarr/napari_ome_zarr/_reader.py", line 108, in f
    for node in nodes:
  File "/Users/wmoore/Desktop/ZARR/ome-zarr-py/ome_zarr/reader.py", line 625, in __call__
    node = Node(self.zarr, self)
  File "/Users/wmoore/Desktop/ZARR/ome-zarr-py/ome_zarr/reader.py", line 53, in __init__
    self.specs.append(Multiscales(self))
  File "/Users/wmoore/Desktop/ZARR/ome-zarr-py/ome_zarr/reader.py", line 286, in __init__
    fmt = format_from_version(version)
  File "/Users/wmoore/Desktop/ZARR/ome-zarr-py/ome_zarr/format.py", line 22, in format_from_version
    raise ValueError(f"Version {version} not recognized")
ValueError: Version 0.5 not recognized

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.24 🎉

Comparison is base (9540832) 84.54% compared to head (7b56cb7) 84.78%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #266      +/-   ##
==========================================
+ Coverage   84.54%   84.78%   +0.24%     
==========================================
  Files          13       13              
  Lines        1475     1472       -3     
==========================================
+ Hits         1247     1248       +1     
+ Misses        228      224       -4     

Impacted Files	Coverage Δ
ome_zarr/data.py	87.12% <100.00%> (+0.12%)	⬆️
ome_zarr/reader.py	86.70% <100.00%> (+0.64%)	⬆️

... and 1 file with indirect coverage changes

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[will-moore]

@joshmoore This look OK to you? Hope to get this in a release soon if no objections?

[joshmoore]

👍 as well as for the quick release.

I assume there's code hanging around that's checking for the missing node data and metadata after the exception which may need to now handle the exception, but those should appear fairly quickly.

With the addition of the schemas, the better longer-term strategy would likely be to use the schema and raise a validation exception