Replace vcf-nav with proper component in Start

[rolfsmeds]

No description provided.

[bwajtr]

Note that we discussed the following: vcf-nav will be integrated to 24.1 as vaadin-side-nav under a feature flag as experimental component.
The plan is to remove vcf-nav from Starter entirely and let the users to opt-in to use the new experimental vaadin-side-nav
If they do not choose to use it (which would be a default option), we will use RouterLinks in the Starter navigation menu instead of vcf-nav