Macro test_binary_field 

macro_rules! test_binary_field {
    ($field:ty, $zeros: expr, $ones: expr, $factors: expr) => { ... };
}

A test_field!-equivalent suite for fields of characteristic 2.

PrimeCharacteristicRing::{halve, div_2exp_u64} are documented to panic unconditionally in characteristic 2, so this replaces test_div_2exp_u64 with test_halve_panics_char2 and test_div_2exp_u64_panics_char2, which pin that panic, and swaps every other halve-dependent (or otherwise characteristic-2-degenerate) check for a characteristic-2-safe sibling (test_ring_with_eq_char2, test_mul_2exp_u64_is_zero_above_e0, test_inverse_char2, test_sqrt_char2, test_powers_collect_char2, test_ring_axioms_proptest_char2, test_field_axioms_proptest_char2).