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).

scripts/setup_devenv/build_dependencies.sh

@@ -220,9 +220,9 @@ function install_yac {
 
 
 function install_all {
-    echo "========================"
-    echo "== building HEALPIX & Co"
-    check_and_install healpix_cxx
+    # echo "========================"
+    # echo "== building HEALPIX & Co"
+    # check_and_install healpix_cxx
     echo "========================"
     echo "== building YAC & Co"
     check_and_install yac