Assess the work to add txs to the Haskell simulator

[nfrisby]

With the abrupt end of the Well-Typed contract, tribal knowledge about the Haskell simulator was lost.

This Issue is my driving motivator to re-establish some mastery of the Haskell simulator.

It is also of interest on its own, since the open design questions of Leios are strongly related to the scheme for allocatings txs into Input Blocks.

Definition of Done: Sketch and estimate the work necessary for Issue #358

[nfrisby]

Currently blocked on a spec for how transactions will flow/evolve into/through the Leios pipeline on Cardano mainnet.