Macro tvix_eval::cmp_op

macro_rules! cmp_op {
    ( $vm:ident, $frame:ident, $span:ident, $op:tt ) => { ... };
    (@order < $ordering:expr) => { ... };
    (@order > $ordering:expr) => { ... };
    (@order <= $ordering:expr) => { ... };
    (@order >= $ordering:expr) => { ... };
}

This macro simplifies the implementation of comparison operations.