Cardano Updates

Since #608, using a `TableConfigOverride` when opening a snapshot has no effect.
This commit restores the feature that we can change the disk cache policy on
snapshot open.

Internally, instead of threading through a modified config to open the snapshot,
we modify the whole `SnapshotMetaData` (replacing the disk cache policy
everywhere) and open the snapshot from that modified metadata.

A first idea we had was to modify a table config while its table is live, but
there are some challenges. Changing a table config when the table is offline
seem to be more straightforward, so that's the approach we took (for now). An
explanation of the challenges can be found in the `*.Config.Override` module.

Bumps [actions/download-artifact](https://github.com/actions/download-artifact) from 4.1.9 to 4.2.1.
- [Release notes](https://github.com/actions/download-artifact/releases)
- [Commits](https://github.com/actions/download-artifact/compare/v4.1.9...v4.2.1)

---
updated-dependencies:
- dependency-name: actions/download-artifact
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Finish switching of index-using tests to ordinary indexes

Implement remainingUnionDebt and supplyUnionCredits

Make run parameters explicit

Empty runs can occur, especially in the merging tree, so it is nice if
MergingRun.new handles them well. This also matches the prototype.

fix: replace mkSnapshotName that returns Maybe with toSnapshotName that errors