[pipeline threadpool] Pass and manage the Executor by user

[xrayw]

Now, there is still create a new threadpool for each pipeline sync.

jedis/src/main/java/redis/clients/jedis/MultiNodePipelineBase.java

Line 93 in e7bf717

executorService = Executors.newFixedThreadPool(MULTI_NODE_PIPELINE_SYNC_WORKERS);

And this pr seems too complex and inflexible. Difficult to meet complex scenarios https://github.com//pull/4070

I have an idea for minimal changes, we can add a method that allows user to pass in the thread pool by themselves

like

public ClusterPipeline pipelined(Executor pipelineExecutor) {
  return new ClusterPipeline((ClusterConnectionProvider) provider, (ClusterCommandObjects) commandObjects, pipelineExecutor);
}

and make some minor modifications to other classes, like ClusterPipeline & MultiNodePipelineBase

This change is minor and can be adapted to any complex user scenario.

Any feedback is welcome. thanks

[ggivo]

Thanks @xrayw for raising this!
This appears to be a duplicate of #4141.
A similar approach was already discussed in PR #4070.

Closing this one to keep the discussion centralized in a single place — please continue the conversation in #4141.