Migrate all exposed / exported zarr3 configs to use chunk encoding version 2

[MichaelBuessemeyer]

Detailed Description

Currently, the default chuck encoding is used: https://zarr-specs.readthedocs.io/en/latest/v3/core/v3.0.html#chunk-key-encoding But migrating from default to v2 would enable us to leave out the c. pretending all zarr3 requests regarding the datasets / datalayers for whose we expose zarr.json configs.

Features where zarr.jsons are written are:

• zarr streaming
• zarr export
• maybe more

To implement this, simply change

 "chunk_key_encoding": {
    "name": "default",
    "configuration": {
      "separator": "."
    }
  },

to

"chunk_key_encoding": {
    "name": "v2",
    "configuration": {
      "separator": "."
    }
  },