[WIP] refactor(homepage): use dynamic plugin config for menu item config

[christoph-jerolimov]

Description

Do not merge, WIP

Which issue(s) does this PR fix

• Fixes #?

PR acceptance criteria

Please make sure that the following steps are complete:

• GitHub Actions are completed and successful
• Unit Tests are updated and passing
• E2E Tests are updated and passing
• Documentation is updated if necessary (requirement for new features)
• Add a screenshot if the change is UX/UI related

How to test changes / Special notes to the reviewer

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[openshift-ci]

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[github-actions]

The image is available at:

• quay.io/janus-idp/backstage-showcase:pr-2007 or
• quay.io/janus-idp/backstage-showcase:pr-2007-19411461