remove LOCK and CAS in bvar counter

[oathdruid]

Is your feature request related to a problem? (你需要的功能是否与某个问题有关?)
bvar::detail::AgentCombiner use LOCK or CAS operation as a general implementation for counter. But when look into specific counters like Adder/Maxer/IntRecorder/LatencyRecorder, the LOCK or CAS operation may be avoidable.

Describe the solution you'd like (描述你期望的解决方法)
some method demonstrated here: use-counter-with-bvar

Describe alternatives you've considered (描述你想到的折衷方案)

Additional context/screenshots (更多上下文/截图)