Add 6 golden files captured from Tailscale SaaS that cover subnet-to-subnet
ACL scenarios where both source and destination are subnet CIDRs. These fill
a complete gap in the existing 92 ROUTES golden files, none of which tested
this pattern.
Scenarios covered:
f10: exact issue #3157 reproduction (disjoint subnets, host aliases)
f11: bidirectional with overlapping big-router
f12: host aliases where dst is a superset route
f13: disjoint subnets, bidirectional
f14: both src and dst overlap on one router
f15: cross-router bidirectional
All 6 pass TestRoutesCompat, confirming headscale matches Tailscale SaaS
behavior for subnet-to-subnet filter rule distribution.
Updates #3157
Updates #3169