Remove more trace/output/demo related constraints from RunNode (#776)

* Remove more trace/output/demo related constraints from RunNode

Whenever a new constraint was needed in `cardano-node` to trace something, it
was added as a super-class constraint of `RunDemo`, which required updating
the `ouroboros-network` package.

A better approach:

In `cardano-node/Cardano/Node/CLI.hs` in `cardano-node`:

```
type DemoTracing blk =
    ( Condense blk
    , Condense [blk]
    , Condense (ChainHash blk)
    , Condense (Header blk)
    , Condense (HeaderHash blk)
    , Condense (GenTx blk)
    )

data SomeProtocol where
  SomeProtocol :: ( RunDemo blk
                  , DemoTracing blk
                  )
               => Consensus.Protocol blk -> SomeProtocol
```

Add `DemoTracing blk` to `app/Run.hs`:

```
handleSimpleNode :: forall blk. (RunDemo blk, DemoTracing blk)
..
```

Now, whenever you need an additional constraint for tracing/demo purposes,
just add it to `DemoTracing`. No changes to the consensus package will be
needed, unless the constraint is not satisfied for a block type.

* Remove left-over Ouroboros.Consensus.Demo.Ledger.Mock

This should have been removed in #727.

ouroboros-consensus/src/Ouroboros/Consensus/Node/Run/Abstract.hs

@@ -26,12 +26,7 @@ import           Ouroboros.Consensus.Protocol.Abstract
 
 import           Ouroboros.Storage.Common (EpochNo, EpochSize)
 
-class ( ProtocolLedgerView blk
-      , ApplyTx blk
-      , Show blk
-      , Show (ApplyTxErr blk)
-      , Show (GenTx blk)
-      ) => RunNode blk where
+class (ProtocolLedgerView blk, ApplyTx blk) => RunNode blk where
 
   nodeForgeBlock         :: (HasNodeState (BlockProtocol blk) m, MonadRandom m)
                          => NodeConfig (BlockProtocol blk)