ManifestStore fails to parse chunk indexes for array keys ending with the letter c.

[sharkinsspatial]

#523 introduced logic to handle ManifestArrays that contain a single scalar which uses the Zarr convention of using the "c" key for handling scalars. It appears that this inadvertently treats all keys ending with "c" as scalars. See b5d764c for an MVE. @maxrjones I don't fully understand the key parsing logic here but if you have some time to circle up Monday I can take a shot a PR for this.

[maxrjones]

🤦‍♂️ my bad. #672 should fix this. Apologies for not giving you a chance at a PR, I'm a bit nervous about getting a release out in time for ESIP and wanted to fix it now.