Fix Brute force failure

[TimSheard]

Fixed broken test, test comparing the brute force DRepDistr computation on the first MockChainState of an epoch to the Pulsed DrepDistr on the final MockhainState of the Epoch.

This failed because we need the intermediate NES in the first state, since the LEDGERS rule changes the NES after the TICK rule runs. To do this we changed the internals of MockChainState from this

data MockChainState era = MockChainState
  { mcsNes :: !(NewEpochState era)
  , mcsLastBlock :: !SlotNo
  , mcsCount :: !Int -- Counts the blocks made
  }

to this

data MockChainState era = MockChainState
  { mcsNes :: !(NewEpochState era)
  , mcsTickNes ::  !(NewEpochState era)
  , mcsLastBlock :: !SlotNo
  , mcsCount :: !Int -- Counts the blocks made
  }

This stores the intermediate NewEpochState, after the TICK rule, but before the LEDGERS rule

Description

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated
• When applicable, versions are updated in .cabal and CHANGELOG.md files according to the
  versioning process.
• The version bounds in .cabal files for all affected packages are updated. If you change the bounds in a cabal file, that package itself must have a version increase. (See RELEASING.md)
• All visible changes are prepended to the latest section of a CHANGELOG.md for the affected packages. New section is never added with the code changes. (See RELEASING.md)
• Code is formatted with fourmolu (use scripts/fourmolize.sh)
• Cabal files are formatted (use scripts/cabal-format.sh)
• hie.yaml has been updated (use scripts/gen-hie.sh)
• Self-reviewed the diff

[lehins]

Beautiful. Simple and elegant