Create a newtype for Value to represented minted/burned tokens

[zliu41]

It has been suggested in https://github.com/IntersectMBO/plutus/pull/5781#issuecomment-2329322923 that among all Value fields in ScriptContext, only txInfoMint could contain negative quantities.

• Check with the ledger team whether this is the case
• If so, it could make sense to make a newtype wrapper to represent txInfoMint.