Add bit_len() function

[jrose]

Previously:

Add methods that return the number of bits necessary to represent an integer in binary to the standard library

Hi internals, Currently, the number of bits necessary to represent an integer in binary to can be obtained by: For unsigned integers: let answer: u16 = 42; // 0b10_1010 assert_eq!(answer.checked_ilog2().map_or(0, |n| n + 1), 6); For signed integers (excluding the sign bit and leading zeros): let n: i16 = -37; // -0b10_0101 assert_eq!(n.unsigned_abs().checked_ilog2().map_or(0, |n| n + 1), 6); Methods for this purpose appear to exist in the standard library of several languages: int.bit_le…