Use sendBatch() instead of sendBatchAsync().get()

[Nandakumar-M]

In TelemetryClient.close(), sendBatchAsync().get() makes the TelemetryThreadPool do the work and current thread waits for it to complete.

When large number of threads are closing connections concurrently using sendBatchAsync().get(), the TelemetryThreadPool gets overloaded (max threads : 10) and this in turn makes SnowflakeConnectionV1.close() a bottleneck.

Instead, sendBatch() can be called directly on the same thread that is closing the connection.

Overview

SNOW-XXXXX

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   Fixes #NNNN

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[Nandakumar-M]

Fixes #665

[sfc-gh-igarish]

@Nandakumar-M Please take action on this old PR or close it.