Add unit test for es v7 bulk processor

[neil-xie]

What changed?
Add unit test for es v7 bulk processor
Change one method name to match naming conventions

Why?
Improve test coverage

How did you test it?
Unit test

Potential risks

Release notes

Documentation Changes

[coveralls]

Pull Request Test Coverage Report for Build 018e1f33-f6cf-4769-a3e6-452c2d0b19ce

Details

• 2 of 4 (50.0%) changed or added relevant lines in 1 file are covered.
• 81 unchanged lines in 17 files lost coverage.
• Overall coverage increased (+0.1%) to 63.911%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
common/elasticsearch/client/v7/client_bulk.go	2	4	50.0%

Files with Coverage Reduction	New Missed Lines	%
common/elasticsearch/client/v7/client_bulk.go	1	92.19%
common/task/weighted_round_robin_task_scheduler.go	2	89.05%
service/history/task/transfer_active_task_executor.go	2	72.51%
service/matching/taskListManager.go	2	80.96%
service/history/task/transfer_standby_task_executor.go	2	87.42%
service/history/shard/context.go	2	66.67%
common/util.go	2	91.69%
service/history/execution/mutable_state_util.go	2	78.48%
common/membership/hashring.go	2	82.23%
service/history/queue/timer_gate.go	3	95.83%

Totals
Change from base Build 018e1f2e-cd91-4a89-a804-d5e16440a906:	0.1%
Covered Lines:	93166
Relevant Lines:	145774

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💛 - Coveralls