Migrate to Zarr 3
Pre-work to #6
This MR has the following:
- Migration to Zarr 3 API while removing the deprecated yet still supported Zarr 2 API usage.
- 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).
Edited by Siddhant Tibrewal