GitHub: T6494: add consolidated ISO test result comment on PR

[c-po]

Change Summary

During PR action to test vyos-1x package by assembling a custom ISO and running all the smoketests, reduce the noise and only add a summary PR comment when all checks passed.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Code style update (formatting, renaming)
• Refactoring (no functional changes)
• Migration from an old Vyatta component to vyos-1x, please link to related PR inside obsoleted component
• Other (please describe):

Related Task(s)

• https://vyos.dev/T6494

Related PR(s)

Component(s) name

Proposed changes

How to test

Automatically generated with a new PR

Checklist:

• I have read the CONTRIBUTING document
• I have linked this PR to one or more Phabricator Task(s)
• I have run the components SMOKETESTS if applicable
• My commit headlines contain a valid Task id
• My change requires a change to the documentation
• I have updated the documentation accordingly

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