Some tests in another repo were broken by tailscale/tailscale#19607.
This fixes them, by finishing off the rest of the migration away from
netmap.NetworkMap on the IPN bus in containerboot.
Containerboot used to rebuild a full NetworkMap-shaped view while
reacting to IPN bus notifications. Now it insteads has its own
netmapState type (immutable) of exactly what it needs to track, and
sends those immutable values around, making cheap edits of new
immutable values when an IPN bus edit arrives.
This should make cmd/containerboot scale to much larger tailnets now too.
Fixes#19852Fixestailscale/corp#42347
Updates #12542
Change-Id: I88adaf061f85f677f954a764935e6654329d75a6
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
364b952d62