Add support for validation of zarr filesets

ATM I believe we are just testing if we can open them and two custom checks (not an empty group and not too deep of hierarchy). [Initial validate support, with --strict option](https://github.com/ome/ome-zarr-py/pull/142/files#top). in ome-zarr-py was recently merged so we should make use of it for our ome .zarrs.

- check how well it works with strict mode on our dandizarrs
- possibly, if needed, propose refactoring in ome-zarr-py to split away analysis from rendering of validation results since the https://github.com/ome/ome-zarr-py/pull/142/files#diff-b50d9715cc6e4017cfc055fd0ed73ecb5d9158e17f4d58ca5b3ba08b89c46657R206 does both
- add into our validation for zarrs