
In f77821fd63
(released in v1.72.0), we made the client tell a DERP server
when the connection was not its ideal choice (the first node in its region).
But we didn't do anything with that information until now. This adds a
metric about how many such connections are on a given derper, and also
adds a bit to the PeerPresentFlags bitmask so watchers can identify
(and rebalance) them.
Updates tailscale/corp#372
Change-Id: Ief8af448750aa6d598e5939a57c062f4e55962be
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>