telemetry/geoprobe: use per-probe TWAMP port and change geoprobe default from 862 to 8925

[ben-dz]

Summary of Changes

• DZD ACL policies block TWAMP replies on port 862 from geoprobe-agents. Change the geoprobe-agent and geoprobe-target default TWAMP reflector port from 862 to 8925, and make the pinger use a per-probe TWAMP port instead of a hardcoded constant.
• Add TWAMPPort field to ProbeAddress so each probe carries both its UDP offset port and TWAMP reflector port.
• Update ParseProbeAddresses to accept host (defaults both ports to 8923/8925) or host:offset_port:twamp_port (both explicit). The old two-field host:port format is rejected as ambiguous.
• Device-to-device TWAMP (port 862) and controller ACL templates are unaffected.

Diff Breakdown

Category	Files	Lines (+/-)	Net
Core logic	4	+56 / -20	+36
CLI/config	3	+4 / -4	0
Tests	4	+159 / -91	+68

Most of the diff is mechanical test updates adding TWAMPPort: 8925 to ProbeAddress literals.

Key files (click to expand)