wb | simplify and remove dependencies

[fmaste]

Description

• Remove support for the podman Nomad plugin (workbench's -nomadpodman sub-backend).
• Remove uses of the Nomad version that comes from nixpkgs. Always use SRE patched version of Nomad based on version 1.6.3 that adds support for Nix dependencies.
• Remove publish functionality dependencies while the new infrastructure is decided.
• Cleanups: remove vault, nix2container and simplify some of the code.
• Update container-enabled OpenSSH to the latest version.

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated. These may include:
  • golden tests
  • property tests
  • roundtrip tests
  • integration tests
    See Runnings tests for more details
• Any changes are noted in the CHANGELOG.md for affected package
• The version bounds in .cabal files are updated
• CI passes. See note on CI. The following CI checks are required:
  • Code is linted with hlint. See .github/workflows/check-hlint.yml to get the hlint version
  • Code is formatted with stylish-haskell. See .github/workflows/stylish-haskell.yml to get the stylish-haskell version
  • Code builds on Linux, MacOS and Windows for ghc-8.10.7 and ghc-9.2.7
• Self-reviewed the diff

Note on CI

If your PR is from a fork, the necessary CI jobs won't trigger automatically for security reasons.
You will need to get someone with write privileges. Please contact IOG node developers to do this
for you.

[mgmeier]

Excellent work, thank you @fmaste