Make Write.Tx.BalanceSpec default to running in all recent eras

[Anviking]

• Run BalanceSpec tests in all recent eras (forall era. IsRecentEra => RecentEra era) per default.

We now have

spec :: Spec
spec = do
    forAllRecentEras $ \era -> do
        spec_balanceTx era
        spec_updateTx era

    -- The exact test expectations depend on the test data which was generated
    -- in either Alonzo or Babbage. Only running in Babbage should be fine for
    -- now. When Babbage is dropped we could regenerate the test txs.
    spec_estimateSignedTxSize RecentEraBabbage

We also now have goldens for each era; one in a babbage directory, and one in a conway directory.

Fixes #4882

[abailly]

Is still relevant?

[Anviking]

This should be done. I've created #4882 for proper scheduling. Closing this PR for now.

[Anviking]

Marginally more expensive than in babbage: 0.169857 — looks right.

A con with separating the goldens by era like this is that we won't ever get GH diffs between eras. Not unless we add latest/pingPong_1 separately from conway/pingPong_1 and babbage/pingPong_1, which I concidered but didn't end up doing now.