[UI] Provide a table showing all child executions started from a given parent flow using Subflow or ForEachItem task

[anna-geller]

Feature description

User request: "Flow A (foreachitem x 100 items) -> Flow B -> Flow C.
In that case I have 1 flow A execution, 100 flow B executions, and 100 flow C executions. I just want a place I can see (1 + 100 + 100) = 201 flows all grouped under one unique identifier"

Possible implementation in the UI

On the Executions page, allow to filter for a specific execution, and then add a checkbox "show child executions", showing all downstream subflow executions created via Subflow and ForEachItem task

On the backend side, the parent may add some UUID and propagate it to all child executions

[anna-geller]

the use case will be solved by system_correlationId label as discussed here #2059 (comment)