Give proper implmementations to the functions in AbstractFunctions

[Soupstraw]

The HSAbstractFunctions implementation for AbstractFunctions has a lot of placeholder functions. These functions should be implemented properly or passed to the spec from the implementation via ExternalFunctions.

formal-ledger-specifications/src/Ledger/Conway/Foreign/HSLedger/Core.agda

Lines 204 to 220 in d406853

	instance
	HSAbstractFunctions : AbstractFunctions
	HSAbstractFunctions = record
	{ Implementation
	; txscriptfee = λ tt y → 0
	; serSize = λ v → v
	; indexOfImp = record
	{ indexOfDCert = λ _ _ → nothing
	; indexOfRwdAddr = λ _ _ → nothing
	; indexOfTxIn = λ _ _ → nothing
	; indexOfPolicyId = λ _ _ → nothing
	; indexOfVote = λ _ _ → nothing
	; indexOfProposal = λ _ _ → nothing
	}
	; runPLCScript = λ _ _ _ _ → false
	; scriptSize = λ _ → 0
	}