Correct pif to hif; add apostrophes to distinguish

[lemmon-714]

• imo it should say "lazy hif", as we are in Haskell-land again. I don't know if regular pif is Haskell-land as well; if so, imo should be renamed as well.
• the wrapper is around pif', not pif
• hif is already used in the beginning, renamed to hif'

[L-as]

Where does hif come from?

[lemmon-714]

It is used without explicit definition in the beginning of the file as haskell-if (can't use regular if-then-else because of the then-else, which the pif lacks). Would assume it has the definition

hif :: Bool -> a -> a
hif cond whenTrue whenFalse = if cond then whenTrue else whenFalse

Shall I add it?

[L-as]

Yes please

[cjay]

Superceded by https://github.com/Plutonomicon/plutarch-plutus/pull/608

[L-as]

Thanks for your work!