Function safe_arch::population_extract_u64

#[must_use]pub fn population_extract_u64(a: u64, index: u64) -> u64

This is supported with target feature bmi2 only.

Extract bits from a u64 according to a mask.

assert_eq!(population_extract_u64(0b1001, 0b1111), 0b1001);
assert_eq!(population_extract_u64(0b1001, 0b1110), 0b0100);
assert_eq!(population_extract_u64(0b1001, 0b1100), 0b0010);