Add DecisionTaskStartedEventID to workflowInfo

[longquanzheng]

What changed?
Add DecisionTaskStartedEventID to workflowInfo

Why?
In some use cases, users need to get the eventID for resetting certain activity/timer/etc.
This is the similar to BinaryChecksum which we are currently supporting.

How did you test it?
Existing tests

Potential risks
No

[coveralls]

Pull Request Test Coverage Report for Build 27f52762-e037-41ba-80a8-a3d049506fae

• 2 of 5 (40.0%) changed or added relevant lines in 2 files are covered.
• 13 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.1%) to 71.652%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
internal/workflow.go	0	3	0.0%

Files with Coverage Reduction	New Missed Lines	%
internal/internal_task_pollers.go	2	81.53%
internal/compatibility/response.go	11	48.43%

Totals
Change from base Build 2e827765-7cf1-4470-a352-de8ddaf1cfe7:	0.1%
Covered Lines:	12188
Relevant Lines:	17010

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💛 - Coveralls