getLSBIndex: Replace PoT lookup table with Math.clz32

[liamdon]

The lookup table approach is really neat, but after running some benchmarks it looks like we can get a ~10-15x speedup by using the built-in Math.clz32()

Benchmark

let n = 2;
for (let i = 0; i < 16; i++) {
	getLSBIndex(n);
	n *= 2;
}

Chrome 119

Approach	Second Header
Math.clz32	145M ops/s ± 0.48%
Lookup table	9.8M ops/s ± 0.24% (93.21% slower)

Safari 17.9

Approach	Second Header
Math.clz32	120M ops/s ± 0.24%
Lookup table	12M ops/s ± 0.51%. (89.76% slower)

Math.clz32() Browser support