fake/noop implementations of SnowflakeStreamingIngestClient and SnowflakeStreamingIngestChannel

[jdcaperon]

Is there any interest in a contribution of a set of fakes for the SnowflakeStreamingIngestClient and channel in order to support easier testing for downstream users. Understandably it adds overhead for support so I can understand a lack of interest. I'd be happy to upstream some simple internal fakes I am building for testing if that's interesting.

I see that there is support for a form of testing mode in the builder of the of client but AFAICT this does not extend to channels.

snowflake-ingest-java/src/main/java/net/snowflake/ingest/streaming/SnowflakeStreamingIngestClientFactory.java

Lines 48 to 51 in 5e93b3d

	public Builder setIsTestMode(boolean isTestMode) {
	this.isTestMode = isTestMode;
	return this;
	}

Largely the fakes themselves can be very simple as the API itself is rather plain. The only possible complication is the table schema API since there is no obvious construction for it. https://github.com/snowflakedb/snowflake-ingest-java/blob/master/src/main/java/net/snowflake/ingest/streaming/SnowflakeStreamingIngestChannel.java#L282-L289

In particular fakes become very useful when working with many channels as mocking channels that are dynamically created but also dynamically closed etc is quite tedious.

Happy to hear thoughts and suggestions cheers.