[code-coverage] Add more test cases for HandleDecisionTaskCompleted

[ketsiambaku]

What changed?

• Added more tests cases for HandleDecisionCompleted

• Separated the mock DomainCache setup from the shared mock setup function because some tests needed a different mock DomainCache setup

• Also separated the default GetWorkflowExecution call from the shared mock setup

Why?
Improve unit tests in service/history/decision

How did you test it?
unit tests

Potential risks

Release notes

Documentation Changes

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.08%. Comparing base (b567432) to head (7d01398).

Additional details and impacted files

see 12 files with indirect coverage changes

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[coveralls]

Pull Request Test Coverage Report for Build 018f2b96-f8db-49f8-ba8a-22ca0c4f830b

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 66 unchanged lines in 14 files lost coverage.
• Overall coverage increased (+0.04%) to 67.894%

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Files with Coverage Reduction	New Missed Lines	%
common/task/weighted_round_robin_task_scheduler.go	1	89.05%
service/history/task/transfer_standby_task_executor.go	2	86.21%
service/history/handler/handler.go	2	54.72%
service/history/task/transfer_active_task_executor.go	2	72.85%
service/matching/matcher.go	2	90.72%
common/membership/hashring.go	2	84.69%
common/persistence/historyManager.go	2	66.67%
common/persistence/statsComputer.go	3	96.07%
service/frontend/api/handler.go	4	62.13%
service/history/task/fetcher.go	5	85.57%

Totals
Change from base Build 018f2b71-576a-49d5-a987-f479b76298cc:	0.04%
Covered Lines:	99690
Relevant Lines:	146831

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💛 - Coveralls