Support DNS SRV Records within Ringpop

[lindleywhite]

This PR adds the ability to configure an additional DNS method to reference DNS SRV records. This allows the initial service discovery of services to lookup hosts based on SRV records instead of having fixed ports within the host configuration.

Cadence is required to have fixed ports when configuring it mainly because it is expected to be hosted on primary VMs. However, when you deploy Cadence to a containerized environment you may not be able to fix ports to hosts and would rather have dynamic discoverability.

The tests are supplied with the code. The code just extends what is already there.

The worst case would be that the net.DefaultResolver can not lookup SRV records and thus the server components erring out on startup.

Release notes
Cadence can now support DNS SRV records within the configuration.

Documentation Changes
This could be added as an option within the ringpop configuration. Please advise.

[CLAassistant]

All committers have signed the CLA.

[emrahs]

@mantas-sidlauskas

[coveralls]

Pull Request Test Coverage Report for Build f3484cc7-2d30-4150-9699-f5288b7521bf

• 53 of 59 (89.83%) changed or added relevant lines in 1 file are covered.
• 181 unchanged lines in 21 files lost coverage.
• Overall coverage decreased (-0.08%) to 56.849%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
common/config/ringpop.go	53	59	89.83%

Files with Coverage Reduction	New Missed Lines	%
common/task/weightedRoundRobinTaskScheduler.go	1	89.64%
service/history/execution/mutable_state_task_refresher.go	1	73.82%
client/history/client.go	2	40.3%
client/history/metricClient.go	2	45.94%
common/types/mapper/thrift/shared.go	2	63.43%
service/history/handler.go	2	48.42%
service/history/queue/timer_queue_processor.go	2	58.8%
service/matching/matcher.go	2	91.46%
common/cache/lru.go	3	90.73%
common/persistence/nosql/nosqlplugin/cassandra/workflow.go	3	55.49%

Totals
Change from base Build fc6b58f8-7517-4e22-ad79-b3b4ec4f0150:	-0.08%
Covered Lines:	82306
Relevant Lines:	144781

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💛 - Coveralls