Redo field updates for faster compile

[TimSheard]

Field updates like

 foo {field1 = exp }

Seem to take forever to compile if 'exp' has a complicated type.
Empirical analysis shows that replacing them with simple update functions can dramatically speed things up
for example.

update1 f = \ x -> (x{field1 = f (field1 x)})

we recombined Test.Cardano.Ledger.Generic.GenState.Types, Test.Cardano.Ledger.Generic.GenState.GenScript, and Test.Cardano.Ledger.Generic.GenState.Generate into Test.Cardano.Ledger.Generic.GenState

we also redid Test.Cardano.Ledger.Generic.TxGen

cardano-ledger-test now cuts approximately 20 minutes from compile time.

[lehins]

I am glad that you found this weird compiler performance regression. Waiting for 5 minutes for a module to be compiled was a little too much.