optimize seata-client TM&RM netty eventloop

[funky-eyes]

Why you need it?

构建多个eventloopgroup时，会构建对应的平台线程，会增加线程切换的开销，而TM和RM都属于client，如果一个应用恰好是TM和RM正好可以降低额外的线程数。
When building multiple EventLoopGroups, corresponding platform threads are created, which increases the overhead of context switching. Since both TM and RM are clients, if an application happens to be both TM and RM, it can reduce the number of additional threads.

How it could be?

A clear and concise description of what you want to happen. You can explain more about input of the feature, and output of it.

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[zzzk1]

Hi @funky-eyes, can i pick up this ticket?

[funky-eyes]

Hi @funky-eyes, can i pick up this ticket?

Of course, looking forward to your PR.