Cardano Updates

This PR is to fix for the equivalent test criteria in
marconi-chain-index unit tests.

[PLT-1536]

- fix error: Class extends value undefined is not a constructor or null

4468: Backport fixes for 4465 to release/cardano-node-1.35.x branch r=coot a=coot

# Description

Cherry pick commits from #4467.

# Checklist

- Branch
    - [ ] Commit sequence broadly makes sense
    - [ ] Commits have useful messages
    - [ ] The documentation has been properly updated
    - [ ] New tests are added if needed and existing tests are updated
    - [ ] Any changes affecting Consensus packages must have an entry in the appropriate `changelog.d` directory created using [`scriv`](https://github.com/input-output-hk/scriv). If in doubt, see the [Consensus release process](../ouroboros-consensus/docs/ReleaseProcess.md).
    - [ ] Any changes in the Consensus API (every exposed function, type or module) that has changed its name, has been deleted, has been moved, or altered in some other significant way must leave behind a `DEPRECATED` warning that notifies downstream consumers. If deprecating a whole module, remember to add it to `./scripts/ci/check-stylish.sh` as otherwise `stylish-haskell` would un-deprecate it.
    - [ ] If this branch changes Network and has any consequences for downstream repositories or end users, said changes must be documented in [`interface-CHANGELOG.md`](../docs/interface-CHANGELOG.md)
    - [ ] If serialization changes, user-facing consequences (e.g. replay from genesis) are confirmed to be intentional.
- Pull Request
    - [ ] Self-reviewed the diff
    - [ ] Useful pull request description at least containing the following information:
      - What does this PR change?
      - Why these changes were needed?
      - How does this affect downstream repositories and/or end-users?
      - Which ticket does this PR close (if any)? If it does, is it [linked](https://docs.github.com/en/issues/tracking-your-work-with-issues/linking-a-pull-request-to-an-issue)?
    - [ ] Reviewer requested


Co-authored-by: Karl Knutsson <[email protected]>
Co-authored-by: Marcin Szamotulski <[email protected]>

Make it an Either String Filepath so the left case signifies a builtin.

chore: document preview usage in readme

test: concurrent users metrics

Signed-off-by: Chris Gianelloni <[email protected]>

Co-authored-by: Michael Peyton Jones <[email protected]>