System sites initialization process must be able to handle the linkAccess spec option

[fgiorgetti]

Is your feature request related to a problem? Please describe. Today, if a system site is meant to allow incoming connections from other Skupper sites, it has to provide a RouterAccess, with pre-defined ports.

Describe the solution you'd like Along with that, it would be nice if the initialization process could handle the Site.spec.linkAccess flag and generate a RouterAccess with ports being defined dynamically based on availability.

This should also apply to system bundles, at installation time.