Add prometheus support to cardano-testnet

[isovector]

Description

This PR adds a new --enable-tracer option to cardano-testnet, which when set starts up cardano-tracer and forwards its socket to every node in the testnet. In addition, it also sets up forwarding on the node configuration file so that nodes will actually send data to the tracer.

Fixes #6490

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 Running tests for more details
• Any changes are noted in the CHANGELOG.md for affected package
  • cardano-node-chairman, cardano-submit-api and cardano-testnet instead need a
    changelog fragment in <package>/.changes/, because their CHANGELOG.md is generated
    from fragments at release time. Copy _TEMPLATE.yml from that directory, or run
    nix run github:input-output-hk/cardano-dev#herald -- new
• 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-9.6 and ghc-9.12
• 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.