T5412: Add support for extending config-mode dependencies in add-on packages

[jestabro]

Change Summary

Add support for adding supplemental entries to the config-mode-dependencies dict, outside of the native vyos-1x build. This is to allow definitions within an add-on package, similar to the extension of the xml cache for add-on interface-definitions (https://vyos.dev/T5403).

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/T5412

Component(s) name

Proposed changes

How to test

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

[jestabro]

@Mergifyio backport sagitta

[mergify]

backport sagitta

✅ Backports have been created

• #2315 T5412: Add support for extending config-mode dependencies in add-on packages (backport #2216) has been created for branch sagitta