Add quickcheck state machine tests

[kderme]

This is a follow up pr to test #1266

These tests generate a list of symbolic commands like these

data Command r
    = RollForward Int
    | RollBack (Maybe BlockNo)
    | StopDBSync
    | StartDBSync
    | AssertBlockNo (Maybe BlockNo)

The commands are translated into real commands. For example RollForward Int will forge a new block that fits on the current chain. These real commands are executed against db-sync using the mock chain-sync server. The symbolic commands are exxecuted against a vesy simplistic Model of db-sync which looks like this:

data Model r = Model
    { serverTip :: Maybe BlockNo
    , dbSyncTip :: Maybe BlockNo
    , dbSynsIsOn :: Bool
    }
    deriving stock (Generic, Show)

Finally a number of postconditions are checked.