Add WorkflowIdConflictPolicy in child workflow options

[AndresBena19]

Is your feature request related to a problem? Please describe.
No

Describe the solution you'd like
.setWorkflowIdConflictPolicy were already added to WorkflowOptions but is not available for ChildWorkflowOptions

Reference:

• Add setWorkflowIdConflictPolicy #2055

[Quinn-With-Two-Ns]

WorkflowIdConflictPolicy is not supported on Child workflows by the Temporal Server. The option would need to be supported by the Temporal Server before it could be exposed on the SDK.

https://github.com/temporalio/api/blob/5862ec7755d8c30577d76c335622b0147590e3fe/temporal/api/command/v1/message.proto#L203

[Quinn-With-Two-Ns]

I created a feature issue to track this work temporalio/features#558.