No semantic tokens in where clauses and for poly types

[thetarnav]

foo :: proc (a: $T/[2]$S) -> T // <- `T` has no semantic token and cannot go to definition
    where intrinsics.type_is_numeric(S)
    //         ^           ^         ^
    //      no semantic tokens       |
    //                      no semantic tokens, go to def does not work
{
    when intrinsics.type_is_numeric(S) {
        //                          ^
        return T{} //  <-- no semantic tokens, go to def does not work
    }
}

Interestingly I already made an issue for where clauses before: #446