Improve UnsafeBytes with Go 1.20+

[Fenny]

func UnsafeBytes(s string) []byte {
    if s == "" {
        return nil
    }
    return (*[MaxStringLen]byte)(unsafe.Pointer(
        (*reflect.StringHeader)(unsafe.Pointer(&s)).Data),
    )[:len(s):len(s)]
}
//Benchmark_UnsafeBytes/unsafe-24                 1000000000               0.8708 ns/op          0 B/op          0 allocs/op
//Benchmark_UnsafeBytes/unsafe-24                 1000000000               1.043 ns/op           0 B/op          0 allocs/op
//Benchmark_UnsafeBytes/unsafe-24                 1000000000               0.8187 ns/op          0 B/op          0 allocs/op
//Benchmark_UnsafeBytes/unsafe-24                 1000000000               0.7915 ns/op          0 B/op          0 allocs/op

func UnsafeBytes(s string) []byte {
    return unsafe.Slice(unsafe.StringData(s), len(s))
}
//Benchmark_UnsafeBytes/unsafe-24                 1000000000               0.3992 ns/op          0 B/op          0 allocs/op
//Benchmark_UnsafeBytes/unsafe-24                 1000000000               0.3953 ns/op          0 B/op          0 allocs/op
//Benchmark_UnsafeBytes/unsafe-24                 1000000000               0.3975 ns/op          0 B/op          0 allocs/op
//Benchmark_UnsafeBytes/unsafe-24                 1000000000               0.3997 ns/op          0 B/op          0 allocs/op