Stop using sleep timeouts for Linux futex-based SpinLock
Stop using sleep timeouts for Linux futex-based SpinLock

Timeouts were once necessary when the SpinLock Unlock used an atomic
store and could therefore have a race and a missed wakeup, however,
the Unlock path now uses an atomic exchange, so the missed wakeup
cannot happen.

Fixes #1179

PiperOrigin-RevId: 452047517
Change-Id: I844944879b51b7f7ddac148e063a376cddd0d05a

abseil/abseil-cpp,abseil/abseil-cpp,abseil/abseil-cpp,abseil/abseil-cpp