all: move network monitoring from wgengine/monitor to net/netmon

We're using it in more and more places, and it's not really specific to
our use of Wireguard (and does more just link/interface monitoring).

Also removes the separate interface we had for it in sockstats -- it's
a small enough package (we already pull in all of its dependencies
via other paths) that it's not worth the extra complexity.

Updates #7621
Updates #7850

Signed-off-by: Mihai Parparita <mihai@tailscale.com>

tstest/integration/tailscaled_deps_test_darwin.go

@@ -24,6 +24,7 @@ import (
 	_ "tailscale.com/net/dns"
 	_ "tailscale.com/net/dnsfallback"
 	_ "tailscale.com/net/interfaces"
+	_ "tailscale.com/net/netmon"
 	_ "tailscale.com/net/netns"
 	_ "tailscale.com/net/proxymux"
 	_ "tailscale.com/net/socks5"
@@ -47,7 +48,6 @@ import (
 	_ "tailscale.com/version"
 	_ "tailscale.com/version/distro"
 	_ "tailscale.com/wgengine"
-	_ "tailscale.com/wgengine/monitor"
 	_ "tailscale.com/wgengine/netstack"
 	_ "tailscale.com/wgengine/router"
 )

tstest/integration/tailscaled_deps_test_freebsd.go

@@ -24,6 +24,7 @@ import (
 	_ "tailscale.com/net/dns"
 	_ "tailscale.com/net/dnsfallback"
 	_ "tailscale.com/net/interfaces"
+	_ "tailscale.com/net/netmon"
 	_ "tailscale.com/net/netns"
 	_ "tailscale.com/net/proxymux"
 	_ "tailscale.com/net/socks5"
@@ -47,7 +48,6 @@ import (
 	_ "tailscale.com/version"
 	_ "tailscale.com/version/distro"
 	_ "tailscale.com/wgengine"
-	_ "tailscale.com/wgengine/monitor"
 	_ "tailscale.com/wgengine/netstack"
 	_ "tailscale.com/wgengine/router"
 )

tstest/integration/tailscaled_deps_test_linux.go

@@ -24,6 +24,7 @@ import (
 	_ "tailscale.com/net/dns"
 	_ "tailscale.com/net/dnsfallback"
 	_ "tailscale.com/net/interfaces"
+	_ "tailscale.com/net/netmon"
 	_ "tailscale.com/net/netns"
 	_ "tailscale.com/net/proxymux"
 	_ "tailscale.com/net/socks5"
@@ -47,7 +48,6 @@ import (
 	_ "tailscale.com/version"
 	_ "tailscale.com/version/distro"
 	_ "tailscale.com/wgengine"
-	_ "tailscale.com/wgengine/monitor"
 	_ "tailscale.com/wgengine/netstack"
 	_ "tailscale.com/wgengine/router"
 )

tstest/integration/tailscaled_deps_test_openbsd.go

@@ -24,6 +24,7 @@ import (
 	_ "tailscale.com/net/dns"
 	_ "tailscale.com/net/dnsfallback"
 	_ "tailscale.com/net/interfaces"
+	_ "tailscale.com/net/netmon"
 	_ "tailscale.com/net/netns"
 	_ "tailscale.com/net/proxymux"
 	_ "tailscale.com/net/socks5"
@@ -47,7 +48,6 @@ import (
 	_ "tailscale.com/version"
 	_ "tailscale.com/version/distro"
 	_ "tailscale.com/wgengine"
-	_ "tailscale.com/wgengine/monitor"
 	_ "tailscale.com/wgengine/netstack"
 	_ "tailscale.com/wgengine/router"
 )

tstest/integration/tailscaled_deps_test_windows.go

@@ -32,6 +32,7 @@ import (
 	_ "tailscale.com/net/dns"
 	_ "tailscale.com/net/dnsfallback"
 	_ "tailscale.com/net/interfaces"
+	_ "tailscale.com/net/netmon"
 	_ "tailscale.com/net/netns"
 	_ "tailscale.com/net/proxymux"
 	_ "tailscale.com/net/socks5"
@@ -56,7 +57,6 @@ import (
 	_ "tailscale.com/version/distro"
 	_ "tailscale.com/wf"
 	_ "tailscale.com/wgengine"
-	_ "tailscale.com/wgengine/monitor"
 	_ "tailscale.com/wgengine/netstack"
 	_ "tailscale.com/wgengine/router"
 )