Vector of literals does not always check values

[bbannier]

When parsing a vector of literals I would expect that after parsing all fields in the vector have the literal value; this is not the case.

public type X = unit {
    xs: (uint8(0))[] foreach {
        assert $$ == 0: "unreachable"
    }
};

$ printf '\x00\x01\x02' | spicy-driver -d foo.spicy
[fatal error] terminating with uncaught exception of type hilti::rt::AssertionFailure: unreachable (foo.spicy:5:9-5:38)

This regressed somewhere in #1313 which has been around since 1.7.0.