db-synthesizer does not use `ExperimentalHardForksEnabled` option

[RenateEilers]

Summary

In #4341 TestEnableDevelopmentHardForkEras has been renamed to ExperimentalHardForksEnabled for cardano-node, but the configuration parser for db-synthesizer hasn't seen this change. As a result, calling db-synthesizer with a configuration file where the option is renamed results in behavior that is different from calling cardano-node with the same config. This unintuitive difference can lead to problems (see e.g. #1071) and time-consuming investigations.

Completion criteria db-synthesizer displays the expected behavior when ExperimentalHardForksEnabled is enabled.

The ideal path to this solution is to separate out the parts of cardano-node and ouroboros-consensus that read node configuration in favor of a shared component. This will prevent any future divergence.

If investigation shows that such a separation would require an unreasonable restrucuring of the current code, it will suffice to update the parsers in ouroboros-consensus to match cardano-node.

[amesgen]

FTR: With #1173 merged, db-synthesizer will "understand" Conway by default.