more efficient & effective CI

[lihuiba]

during CI:

• no need to build & run in debug mode (it's for developers' hands); -O2/3 with assertion (no -g, no -DNDEBUG) in CI is closer to productional env;
• every feasible event engine should be tested for each UT;

[beef9999]

Closed by https://github.com/alibaba/PhotonLibOS/pull/273