protect only the latest same-source providers from autoremove

protect only the latest same-source providers from autoremove

Traditionally all providers are protected providing something as apt
can't know which of them is actually really providing the functionality
for the user ensuring that we don't propose the removal of used stuff,
but that is of course also keeping stuff around which could be removed.

That can cause the collection of multiple old providers until the
provided package is itself no longer needed (e.g. out-of-tree kernel
modules). We combat this by marking providers only from the newest
source package version so that old providers built by older versions of
the same source package can be garbage collected.