See BF-45916

• MozJSScriptEngine::sleep tries to sleep in 1 millisecond slices to not block interrupts.
• It does not take into account time actually slept, only what it asked to sleep and then subtracts that from the remaining time to sleep. The result is a compounding sleep error per millisecond of requested sleep time, exacerbated by coarse clock granularity and system load.
• On recent passing systems, the 2s sleep requested in max_time_ms.js takes ~4.5s. Since the clock granularity on windows systems are roughly 3.5ms, it means an immediate 2.5ms unaccounted time per 1ms requested. The same test runs in ~7.5-9s.