Avoid branching on "translateUpperBoundForPlutusScripts" protocol version

[lehins]

It will provide more clarity and code readability if we reimplement transValidityInterval for Conway with new translation and old translation for pre-Conway eras:

cardano-ledger/eras/alonzo/impl/src/Cardano/Ledger/Alonzo/Plutus/TxInfo.hs

Lines 228 to 239 in b7f6382

	transValidityInterval _ protVer epochInfo systemStart = \case
	ValidityInterval SNothing SNothing -> pure PV1.always
	ValidityInterval (SJust i) SNothing -> PV1.from <$> transSlotToPOSIXTime i
	ValidityInterval SNothing (SJust i) -> do
	t <- transSlotToPOSIXTime i
	pure $
	if HardForks.translateUpperBoundForPlutusScripts protVer
	then
	PV1.Interval
	(PV1.LowerBound PV1.NegInf True)
	(PV1.strictUpperBound t)
	else PV1.to t

This would effectively remove the need for standalone translateUpperBoundForPlutusScripts function

[danbaruka]

I’d like to work on this issue if it’s still available. Let me know if there are any constraints I should be aware of before starting.

[lehins]

Hi @danbaruka
Sorry for not responding earlier, I just saw your message.
By all means, feel free to tackle this task if you are interested in working on it. We love having outside contributors.
There aren't really any constraints. Implementation will be fairly straightforward. There will be two versions of transValidityInterval function: one in Alonzo era and one in Conway era and neither one of them will accept protocol version as an argument.

[danbaruka]

What i did is:

• Implement Conway-specific transValidityInterval with new translation logic (strict upper bound, no protocol version branching).
• Update Conway EraPlutusTxInfo instances to use the new function.
• Refactor Alonzo transValidityInterval to always use pre-Conway logic (no protocol version argument or branching).
• Remove protocol-version-based branching and all references to hardforkConwayTranslateUpperBoundForPlutusScripts.
• Remove the function hardforkConwayTranslateUpperBoundForPlutusScripts from Alonzo.Era.
• Ensure all code is era-split and clear for Plutus validity interval translation.