bench: Remove dependency on microlens

This just unfolds the definition of (^.) in terms of
Control.Applicative.Const in order to evade the import of the Lens
module and link to the microlens package. The lens getter appears to be
the sole accessor from data abstraction techniques used i.e. the import
and export of the Shelley TransitionConfig as an abstract type by
Cardano.Ledger.Api.Transition, so the explicitness and readability of
the dependency removal are unfortunately limited.

bench/tx-generator/src/Cardano/TxGenerator/Setup/NodeConfig.hs

@@ -8,15 +8,15 @@ module Cardano.TxGenerator.Setup.NodeConfig
        (module Cardano.TxGenerator.Setup.NodeConfig)
        where
 
+import           Control.Applicative (Const (Const), getConst)
 import           Control.Monad.Trans.Except (runExceptT)
 import           Data.Bifunctor (first)
 import           Data.Monoid
-import           Lens.Micro ((^.))
 
 import qualified Ouroboros.Consensus.Cardano as Consensus
 
 import           Cardano.Api (BlockType (..), ProtocolInfoArgs (..))
-import qualified Cardano.Ledger.Api.Transition as Ledger
+import qualified Cardano.Ledger.Api.Transition as Ledger (tcShelleyGenesisL)
 import           Cardano.Node.Configuration.POM
 import           Cardano.Node.Handlers.Shutdown (ShutdownConfig (..))
 import           Cardano.Node.Protocol.Cardano
@@ -32,7 +32,7 @@ import           Cardano.TxGenerator.Types
 -- as this guarantees proper error handling when trying to create a non-Cardano protocol.
 getGenesis :: SomeConsensusProtocol -> ShelleyGenesis
 getGenesis (SomeConsensusProtocol CardanoBlockType proto)
-    = transCfg ^. Ledger.tcShelleyGenesisL
+    = getConst $ Ledger.tcShelleyGenesisL Const transCfg
   where
     ProtocolInfoArgsCardano Consensus.CardanoProtocolParams
       { Consensus.ledgerTransitionConfig = transCfg

bench/tx-generator/tx-generator.cabal

@@ -120,7 +120,6 @@ library
                       , generic-monoid
                       , ghc-prim
                       , io-classes
-                      , microlens
                       , mtl
                       , network
                       , network-mux