docs(vms): document per-interface packet capture stop and interface names

[GhostofGoes]

Description

Documents the phenix vm capture start/stop CLI support for specifying a VM network interface by name (as declared in the experiment topology, e.g. IF0) in addition to index, and for stopping a single interface's capture without affecting other captures running on the same VM.

This documents the behavior introduced in sandialabs/sceptre-phenix#395, which is itself blocked on sandia-minimega/minimega#1632 (not yet merged). Added a note in the docs calling out that the single-interface stop requires that minimega support.

Related Issue

N/A — see sandialabs/sceptre-phenix#395

Type of Change

• Bugfix
• New feature
• Documentation update
• Other (please describe):

Checklist

• This PR conforms to the process detailed in the Contributing Guide.
• I have included no proprietary/sensitive information in my code.
• I have performed a self-review of my code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have tested my code.

Additional Notes

• make lint (prek run --all-files) passes.
• Tracks sandialabs/sceptre-phenix#395, which is a draft pending sandia-minimega/minimega#1632. This docs PR can be merged independently since it only updates the CLI usage reference and calls out the minimega version requirement.