time: use bit manipulation instead of modulo (#4480)
time: use bit manipulation instead of modulo (#4480)

time: resolve TODO

## Motivation

Existing `TODO` comment in `src/time/driver/wheel/level.rs`.

## Solution

`level_range()` always return a strictly positive power of 2. If `b` is a
strictly positive power of 2, `a - (a % b)` is equal to `a & !(b - 1)`.


tokio-rs/tokio,tokio-rs/tokio