[#830] Forbid parameter prefix root annotations

Description

Problem: As per jakarta's changelog for Michelson:

Annotating the parameter toplevel constructor to designate the root entrypoint is now forbidden. Put the annotation on the parameter type instead. E.g. replace parameter %a int; by parameter (int %a);

Solution: Change our parser to behave likewise. Update test contracts using the forbidden syntax.

Related issue(s)

Resolves #830 (closed)

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