Switch `TxBody` to a data family

[lehins]

One of the most important causes for a new era is any change to the body of a transaction. For this reason, it would make more sense for TxBody type family to be converted to a data family. It will give us injectivity out of the box and will allow us for creating general type class instances.

For example:

Instead of having a separate type:

cardano-ledger/eras/alonzo/impl/src/Cardano/Ledger/Alonzo/TxBody/Internal.hs

Line 214 in 4962396

newtype AlonzoTxBody era = MkAlonzoTxBody (MemoBytes (AlonzoTxBodyRaw era))

and instance definition:

cardano-ledger/eras/alonzo/impl/src/Cardano/Ledger/Alonzo/TxBody/Internal.hs

Line 229 in 4962396

type TxBody AlonzoEra = AlonzoTxBody AlonzoEra

We would get:

  newtype TxBody AlonzoEra = MkAlonzoTxBody (MemoBytes (AlonzoTxBodyRaw era))
    deriving (ToCBOR, Generic)
    deriving newtype (SafeToHash)