Update to ledger-api-1.6 and ledger-conway-1.9

[amesgen]

Next major ledger release should be soon-ish and will likely be not too different from what is being integrated here.

• Most of the diff is due to integrating the new TransitionConfig concept from Ledger, see Implement EraTransition cardano-ledger#3737.
  • Every Shelley-based era XEra c has a TransitionConfig (XEra c) that contains all Genesis information up until this era. In particular, one can get all previous TranslationContexts and TransitionConfigs up until this era from it.
  • They can be used to register initial funds and staking (benchmarking features whose implementation has now been moved to Ledger), and to create initial Shelley ledger states for pure Shelley-based chains.
  • We could keep the current interface to protocolInfoCardano the same (by assembling a Conway TransitionConfig from the given TranslationContexts), but Ledger wants to push the construction of the TransitionConfig downwards to Node etc (eg in order to be able to add more information to it, or even consolidate all Genesis files into one).
    This also actually makes things easier on our end, as this allows us to simplify the ProtocolTransitionParams.
• Ledger state serialization and the Conway Genesis file format changed.

[lehins]

My 2¢ on the subject of initial configuration from the perspective of a user, having dealt with it on numerous occasions. It doesn't need to be that complicated. The simpler the better.