Add more explicit `--bind-address` and `--bind-port` flags to the `tailscale netcheck` CLI to give users control over UDP probes' source IP and UDP port.
This was already supported in a less documented manner via the` TS_DEBUG_NETCHECK_UDP_BIND` environment variable. The environment variable reference is preserved and used as a fallback value in the absence of these new CLI flags.
Updates tailscale/corp#36833
Signed-off-by: Amal Bansode <amal@tailscale.com>
Amal Bansode