Add additional metadata

[richfitz]

We need a location entry for orderly2 to be able to interact with the outpack archive, at least for things like migrating data. This PR adds the "local" location, which orderly treats specially (to the point where it cannot add it).

Metadata on initialisation, after this PR:

{
  "core": {
    "hash_algorithm": "sha256",
    "path_archive": null,
    "use_file_store": true,
    "require_complete_tree": false
  },
  "location": [
    {
      "name": "local",
      "type": "local",
      "args": {}
    }
  ]
}

Currently the location section is the empty list.

[plietar]

This is unrelated to this PR, but in the past I've done explicit PRs for bumping the version number, following https://github.com/mrc-ide/outpack_server?tab=readme-ov-file#releasing

I would be fine with using the same workflow we do in our R stuff, and bump the version on every commit. We'd want to tweak our CI to a) ensure the version has been bumped and b) push to PyPI on every push to main, not just on tags.