Refactor PeerChooserFactory out of DispatcherProvider

[vytautas-karpavicius]

What changed?
Refactored DNS peer chooser functionality out of DispatcherProvider.

Why?
This is a preparation step before merging DispatcherProvider into rpc.Factory.

How did you test it?
Existing tests.

• Added unit tests for the refactored part.

Potential risks

Release notes

Documentation Changes

[coveralls]

Pull Request Test Coverage Report for Build a8ad1f55-8f80-4c97-bb6f-7829520f5148

• 25 of 28 (89.29%) changed or added relevant lines in 4 files are covered.
• 20 unchanged lines in 9 files lost coverage.
• Overall coverage increased (+0.02%) to 56.476%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
cmd/server/cadence/server.go	0	3	0.0%

Files with Coverage Reduction	New Missed Lines	%
service/history/execution/mutable_state_task_refresher.go	1	73.82%
common/persistence/historyManager.go	2	66.33%
common/task/weightedRoundRobinTaskScheduler.go	2	89.12%
common/types/mapper/thrift/shared.go	2	64.65%
service/history/execution/mutable_state_builder.go	2	69.77%
service/history/queue/transfer_queue_processor.go	2	57.76%
service/history/shard/context.go	2	66.64%
service/history/queue/timer_gate.go	3	95.83%
common/task/fifoTaskScheduler.go	4	83.51%

Totals
Change from base Build ee6fae76-db89-448e-96a6-6baab24744eb:	0.02%
Covered Lines:	80237
Relevant Lines:	142073

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💛 - Coveralls