Add AsyncAppender support

[aaron-ai]

Fixes #362

[codecov-commenter]

Codecov Report

Merging #363 (474d4dc) into master (8aa0ee1) will increase coverage by 25.91%.
The diff coverage is n/a.

@@              Coverage Diff              @@
##             master     #363       +/-   ##
=============================================
+ Coverage     34.78%   60.69%   +25.91%     
+ Complexity      646      645        -1     
=============================================
  Files           220       95      -125     
  Lines         11489     3819     -7670     
  Branches        276      279        +3     
=============================================
- Hits           3996     2318     -1678     
+ Misses         7244     1346     -5898     
+ Partials        249      155       -94     

Flag	Coverage Δ
cpp	?
golang	?
java	60.69% <ø> (-0.09%)	⬇️

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Impacted Files	Coverage Δ
...cketmq/client/java/impl/producer/ProducerImpl.java	29.77% <0.00%> (-1.91%)	⬇️
...e/rocketmq/client/java/impl/ClientSessionImpl.java	78.02% <0.00%> (-1.33%)	⬇️
.../client/java/impl/consumer/SimpleConsumerImpl.java	41.93% <0.00%> (-0.69%)	⬇️
...cketmq/client/java/metrics/ClientMeterManager.java	68.53% <0.00%> (-0.51%)	⬇️
...mq/client/java/impl/consumer/PushConsumerImpl.java	33.19% <0.00%> (-0.14%)	⬇️
...e/rocketmq/client/java/impl/ClientManagerImpl.java	72.90% <0.00%> (ø)
cpp/source/base/ThreadPoolImpl.cpp
cpp/source/stats/include/PublishStats.h
cpp/include/rocketmq/Credentials.h
cpp/source/concurrent/CountdownLatch.cpp
... and 124 more

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