op-mode: T6524: rewrite "release dhcp(v6) interface" to new op-mode format (backport #3733)

[mergify]

Change Summary

Migrate the last legacy op-mode part using vyatta-interfaces.pl to the new Python code base

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/T6524

Related PR(s)

• T6524: remove vyatta-interfaces.pl, no longer required vyatta-cfg-system#223
• T6524: remove node.def files for "release" CLI tree vyatta-op#92

Component(s) name

Proposed changes

How to test

vyos@vyos:~$ release dhcp interface eth0
Release DHCP client on interface eth0...

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 #3733 done by [Mergify](https://mergify.com).

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