Update PyPNM-CMTS Postman collection with Histogram endpoints and refreshed CMTS visualizer scripts

- Add ServingGroup/Downstream/Histogram requests (StartCapture, Status, Cancel, Results) to the CMTS collection
- Use histogram_cmts_operation_id in the Histogram CMTS operation flow
- Sync the Histogram Results visualizer script from the CMTS Histogram visual source
- Refresh synced CMTS Results visualizer scripts in the collection from current visual HTML updates
- Preserve collection JSON formatting/metadata changes from the latest Postman export  - 2026-02-26 15:34:27

Author: mgarcia01752