[code-coverage] clean up tests in history/decision/handler

[ketsiambaku]

What changed?

1. The test functions were using both test suite and subtests which were confusing. The suite would not reset between subtests

TestHandleDecisionTaskFailed
TestHandleDecisionTaskScheduled
TestHandleDecisionTaskStarted

I changed it so these tests only use table format tests

2. I found out that we already have predefined constants service/history/constants for test purposes. So I deleted the ones I created to use the existing ones

Why?
Make the tests easier to use or edit without potentially saving states between subtests

How did you test it?
unit tests

Potential risks

Release notes

Documentation Changes

[coveralls]

Pull Request Test Coverage Report for Build 018f0b06-d43f-4a93-abe3-133e5e038450

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 96 unchanged lines in 13 files lost coverage.
• Overall coverage decreased (-0.05%) to 67.656%

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Files with Coverage Reduction	New Missed Lines	%
common/task/weighted_round_robin_task_scheduler.go	2	89.05%
common/persistence/execution_manager.go	2	83.74%
service/matching/taskListManager.go	2	79.9%
service/history/execution/mutable_state_util.go	2	78.52%
common/persistence/statsComputer.go	2	96.07%
common/persistence/historyManager.go	2	66.67%
service/history/task/fetcher.go	5	85.57%
service/history/task/transfer_standby_task_executor.go	6	86.63%
common/task/fifo_task_scheduler.go	7	82.47%
service/history/task/cross_cluster_task_processor.go	8	80.79%

Totals
Change from base Build 018f0909-5e23-428f-90ff-d01162e02ac3:	-0.05%
Covered Lines:	99081
Relevant Lines:	146448

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💛 - Coveralls