Expose start delay in child workflow options

[bergundy]

Is your feature request related to a problem? Please describe.

The start delay functionality we recently added is only available when starting workflows from a client.
For feature parity, we should expose this option for child workflows as well.

The use case here is to prevent from having to put a long timer (months) at the top of a workflow and force maintaining history compatibility for as long as that workflow lives. This can be done today by starting the workflow from an activity but that loses the parent-child relationship and traceability in the UI.

Describe the solution you'd like

Expose start delay in child workflow options.

Additional context

First we'll need to add support in the API and server and then expose in all of the SDKs.

Per-SDK Tickets

• Go -
• Java -
• Core -
• TypeScript -
• Python -
• .NET -
• PHP -
• Temporal CLI -