Cardano Updates

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/f677051b8dc0b5e2a9348941c99eea8c4b0ff28f' (2022-09-18)
  → 'github:NixOS/nixpkgs/ae1dc133ea5f1538d035af41e5ddbc2ebcb67b90' (2022-09-22)
• Updated input 'rust-overlay':
    'github:oxalica/rust-overlay/0300688a98e053712108d4e22d5bdcf9c9106d8c' (2022-09-21)
  → 'github:oxalica/rust-overlay/6eb90123f46664ffbb550c527f656ba848718af5' (2022-09-24)

chore(deps): bump actions/cache from 2 to 3

chore(deps): bump actions/checkout from 2 to 3

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v2...v3)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Bumps [actions/cache](https://github.com/actions/cache) from 2 to 3.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](https://github.com/actions/cache/compare/v2...v3)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Improve nix setup and fix nix build

Extract from voteplans the `votes_cast` field for each proposal
to include the count of unique wallets to results.

Fix key for `proposal_id` when generating the proposers rewards
directly from the API remote endpoint instead of using local
files.

- build projects with nix on github actions (to catch this problems in
  the future)
- keep github actions and flake.lock up to date by having regular check
  and PRs when there are any new changes.
- ping jormungandr-devops when there are PRs that touch nix related
  stuff
- remove gitignore flake input since it is not needed anymore (plus it
  adds some impurity to the build)

Direnv + some flake cleanup

extend KeyContribution struct