Feature implementation - Enhance Test Plan Clone Functionality to Include Cloning of Child/Sub Test Plans

[VenkatGIT14]

When we clone a Test Plan (TP) using Settings → Clone, the system only clones the selected parent Test Plan. However, any child/sub Test Plans mapped under the parent TP are not included in the cloned structure.
This creates manual effort because we need to recreate or map the child Test Plans again under the newly cloned parent TP.

Real Scenario:
Example hierarchy:

TP‑326: NVMe_42 (parent)
├── TP‑327: Setup
├── TP‑328: EFI
└── TP‑329: Linux

When cloning TP‑326, the UI asks for:

Clone TCs – Clone or link test cases
Parent TP – Set source TP as parent of new TP

After cloning, only:

TP‑361: NVMe_50 (new parent TP)is created.
The expected child/sub TPs (Setup, EFI, Linux) are not automatically cloned.

This breaks the hierarchy and forces manual work.

We want the solution like:
When cloning a parent Test Plan, the system should also:
✔ Clone all child/sub Test Plans associated with the source TP
✔ Assign new TP IDs automatically to each cloned child TP
✔ Preserve the same hierarchical structure under the new parent TP
✔ Optionally include a checkbox in UI:
“Clone child/sub Test Plans also”

This ensures that the entire Test Plan hierarchy is cloned as a complete unit.