[DevTools] feat: display subtree for Activity and dim in hidden mode (#36094)

With this change, Components panel will display subtree of the Activity.
When it is in hidden mode, the subtree will be dimmed.

Added Jest tests and a sandbox case to `react-devtools-shell`.

Demo:


https://github.com/user-attachments/assets/69a2e8d6-585d-4fcd-b57e-e9ae06d0a1b3