This commit adds a command to validate that all the metrics that
are registring in the client are also present in a path or url.
It is intended to be ran from the KB against the latest version of
tailscale.
Updates tailscale/corp#24066
Updates tailscale/corp#22075
Co-Authored-By: Brad Fitzpatrick <bradfitz@tailscale.com>
Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>
