op-mode: T6161: Show container details in JSON format (backport #3171)

[mergify]

Change Summary

Ability to get container details from op-mode in JSON format.

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/T6161

Related PR(s)

Component(s) name

op-mode

Proposed changes

Being able to get container information in a parseable format.
This is on-par with other commands such as show configuration json.

I found that the "raw" versions of these commands already existed in the python scripts, so I just used the existing/unused flags.

I also made some assumptions about node types.

Should be backported to sagitta without any issue as it's non-breaking.

How to test

show container json
show container image json
show container network json

Smoketest result

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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This is an automatic backport of pull request #3171 done by [Mergify](https://mergify.com).