[docs] Added multi-admin documentation to CHIPTool guide. (#23290)
[docs] Added multi-admin documentation to CHIPTool guide. (#23290)

* [docs] Added multi-admin documentation to CHIPTool guide.

Extended CHIPTool guide by multi-admin scenario section,
describing how to open commissioning window on a device
and pair in to the new fabric.

* Addressed review comments
project-chip/connectedhomeip,project-chip/connectedhomeip,project-chip/connectedhomeip,project-chip/connectedhomeip,project-chip/connectedhomeip,project-chip/connectedhomeip