[Improve][SDK] Optimize the implementation of node connection management

[gosonzhang]

Description

Currently, the node management of DataProxy SDK adopts regular node updates and adds node load status mode for management[1].

From the SDK perspective, it can only see the number of nodes in the cluster and the data reporting status of the nodes currently connected to it. Therefore, the connection management is optimized here: randomize the selected nodes and increase the regular forced node selection; monitor the connected nodes to see if too many requests are blocked and whether the sending buffer size is exceeded.

In addition, considering that the initialization may fail when constructing Sender and ClientMgr objects, in order to avoid thread residue, the thread startup and other operations involving possible failures are placed in the start() function.

1. https://github.com/apache/inlong/blob/master/inlong-sdk/dataproxy-sdk/src/main/java/org/apache/inlong/sdk/dataproxy/network/ClientMgr.java

InLong Component

InLong SDK

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