oneshot-event: Add oneshot_primitive

[avdgrinten]

This is a more lightweight alternative to oneshot_event that does not support cancellation.

[avdgrinten]

Benchmark results on my machine:

-----------------------------------------------------------------------------
Benchmark                                   Time             CPU   Iterations
-----------------------------------------------------------------------------
BM_RaiseWait_OneshotEvent                 153 ns          152 ns      4612758
BM_RaiseWait_OneshotPrimitive            31.8 ns         31.8 ns     22245622
BM_WaitRaise_OneshotEvent                 857 ns          856 ns       809939
BM_WaitRaise_OneshotPrimitive             316 ns          316 ns      2021960
BM_WaitTwiceRaise_OneshotEvent           1495 ns         1494 ns       515077
BM_WaitTwiceRaise_OneshotPrimitive        554 ns          554 ns      1326654

[qookei]

Actually, there is one problem, tests fail to build on CI because Google Benchmark is not installed.