mutable-state: copy to persistence round-trip test

[davidporter-id-au]

What changed?
Fixes minor bugs in copy method and adds a small round-trip test

Why?

How did you test it?

Potential risks

Release notes

Documentation Changes

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.33%. Comparing base (2fef3c3) to head (1148129).
Report is 3 commits behind head on master.

Additional details and impacted files

Files	Coverage Δ
service/history/execution/mutable_state_builder.go	59.85% <100.00%> (+1.22%)	⬆️

... and 8 files with indirect coverage changes

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[coveralls]

Pull Request Test Coverage Report for Build 018f6049-1c10-4110-977c-bb78c2ea3202

Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• 50 unchanged lines in 8 files lost coverage.
• Overall coverage decreased (-0.4%) to 68.45%

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Files with Coverage Reduction	New Missed Lines	%
common/task/weighted_round_robin_task_scheduler.go	1	88.06%
common/membership/hashring.go	2	84.69%
common/persistence/statsComputer.go	3	96.07%
service/frontend/api/handler.go	4	62.26%
service/history/task/fetcher.go	4	86.08%
common/task/fifo_task_scheduler.go	7	82.47%
service/history/engine/engineimpl/poll_mutable_state.go	9	74.16%
service/history/task/task_util.go	20	70.57%

Totals
Change from base Build 018f5e8f-a247-406e-9920-f997ba145d18:	-0.4%
Covered Lines:	88018
Relevant Lines:	128588

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💛 - Coveralls

[taylanisikdemir]

did the roundtrip test uncover these missed fields?

[davidporter-id-au]

yes