Make them more regular by having both take an era param, fix the names
and make them both clearly general in the era.

Conversion functions within the API. We'll need both.

Compute the total balance of the proposed transaction. Ultimately a
valid transaction must be fully balanced: that is have a total value
of zero.

Finding the (non-zero) balance of partially constructed transaction
is useful for adjusting a transaction to be fully balanced.

Compute the transaction fee for a proposed transaction, with the
assumption that there will be the given number of key witnesses
(i.e. signatures).

Give an approximate count of the number of key witnesses
(i.e. signatures) a transaction will need.

This more-or-less mirrors the RdmrPtr, which we generally want to hide,
but for some kinds of tx manipulation it is inevitable. In particular we
will need it to be able to provide the execution units for each script
use, and to perform substitutions.

The collectTxBodyScriptWitnesses helper function was previously only
being used within makeShelleyTransactionBody, but with the addition of
the public ScriptWitnessIndex type, it now makes sense to have it use
that and to expose the function.

It also makes it clearer what the types ScriptWitnessIndex and
AnyScriptWitness are for.

Compute the ExecutionUnits needed for each script in the transaction.

This works by running all the scripts and counting how many execution
units are actually used.

That we will use for the auto-balancing tx construction.

This is much like 'makeTransactionBody' but with greater automation to
calculate suitable values for several things.

In particular:

 * It calculates the correct script 'ExecutionUnits' (ignoring the provided
   values, which can thus be zero).

 * It calculates the transaction fees, based on the script 'ExecutionUnits',
   the current 'ProtocolParameters', and an estimate of the number of
   key witnesses (i.e. signatures). There is an override for the number of
   key witnesses.

 * It accepts a change address, calculates the balance of the transaction
   and puts the excess change into the change output.

 * It also checks that the balance is positive and the change is above the
   minimum threshold.

To do this it needs more information than 'makeTransactionBody', all of
 which can be queried from a local node.

Well, in this case supress since it was not helpful.