[fix](s3-client) Fix s3-client max-connection default value which causes s3 to be slow and unable to handle high concurrency in multi-file scenarios. (#58512)

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Cherry-pick #58511 

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Author: kaka11chen

be/src/util/s3_util.cpp

@@ -369,8 +369,7 @@ std::shared_ptr<io::ObjStorageClient> S3ClientFactory::_create_s3_client(
     if (s3_conf.max_connections > 0) {
         aws_config.maxConnections = s3_conf.max_connections;
     } else {
-        // AWS SDK max concurrent tcp connections for a single http client to use. Default 25.
-        aws_config.maxConnections = std::max(config::doris_scanner_thread_pool_thread_num, 25);
+        aws_config.maxConnections = 102400;
     }
 
     aws_config.requestTimeoutMs = 30000;