Fix parsing domain_id in child_info_maps for backward compatibility

[Shaddoll]

What changed?
If domain_id from child_info_maps is empty UUID, we convert it to an empty string.

Why?
For backward compatibility. null uuids loaded from DB are converted to empty UUID, which is a breaking change for us, because the domain_id field is a new field.

How did you test it?
existing test, verify with child workflows created from 0.23.2 release

Potential risks

Release notes

Documentation Changes

[Groxx]

yeah, string comparison may actually be preferable to comparing values here - we do not have or want any zero-valued UUIDs in the database.

[coveralls]

Pull Request Test Coverage Report for Build 4b9da8df-1abd-4229-87c1-afb0f0d706ba

• 1 of 4 (25.0%) changed or added relevant lines in 1 file are covered.
• 127 unchanged lines in 16 files lost coverage.
• Overall coverage decreased (-0.06%) to 56.832%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
common/persistence/nosql/nosqlplugin/cassandra/workflowParsingUtils.go	1	4	25.0%

Files with Coverage Reduction	New Missed Lines	%
common/task/weightedRoundRobinTaskScheduler.go	1	89.64%
client/history/client.go	2	39.33%
client/history/metricClient.go	2	46.37%
common/persistence/executionManager.go	2	76.69%
common/persistence/statsComputer.go	2	95.71%
service/history/handler.go	2	48.56%
common/persistence/nosql/nosqlplugin/cassandra/workflow.go	3	55.49%
service/frontend/workflowHandler.go	4	59.4%
service/history/historyEngine.go	9	71.3%
service/history/shard/context.go	9	65.43%

Totals
Change from base Build a90bd894-b0ad-4845-91ba-e0e9b8bb6e72:	-0.06%
Covered Lines:	82939
Relevant Lines:	145936

---

💛 - Coveralls