NetworkCapabilities: initialize ALL_VALID_CAPABILITIES without loop

This change also removes the MIN_NET_CAPABILITY constant that is not
actually used and can always be re-added in the future (though, I would
imagine that NetworkCapabilities will not be deprecated / removed in
numerical order).

Test: TH
Change-Id: I97ccbc9e915eb74a0ef52c576e16fc8ce8d5b646