Babbage isWellFormed check

[JaredCorduan]

There is a isWellFormed check in the Babbage formal spec, Figure 6: UTxO with witnesses inference rules for Tx, which is not clearly being checked in the implementation. The situation is a bit confusing due to the fact that these checks are spread out in the ledger code base. We need to make sure that we are properly checking everything.

The current state of things seems to be:

scripts

• The function isScriptWellFormed checks if Plutus scripts are well-formed. This check is done implicitly by scripts which are run.
• The isScriptWellFormed check is wrapped in the ledger code by validScript.
• validScript is only called to validate the auxiliary data. (for example, see here in Alonzo).
• We are not checking that script references are well-formed.
• We are not checking that failed scripts (which are marked as thus in the transaction) are well-formed. This should be a phase 1 failure.

datums

• Datums are completely guarded by the wire format, including the new inline datums in babbage.

Action items:

• check the details above
• fix the two missing checks above
• find a coherent way to document that we are doing this check. it probably needs at least a comment in the UTXOW rule.