safesocket: remove ConnectionStrategy (#10662)

This type seems to be a migration shim for TCP tailscaled sockets
(instead of unix/windows pipes). The `port` field was never set, so it
was effectively used as a string (`path` field).
Remove the whole type and simplify call sites to pass the socket path
directly to `safesocket.Connect`.

Updates #cleanup

Signed-off-by: Andrew Lytvynov <awly@tailscale.com>

tstest/integration/integration_test.go

@@ -1226,9 +1226,8 @@ func (n *testNode) Ping(otherNode *testNode) error {
 // over its localhost IPC mechanism. (Unix socket, etc)
 func (n *testNode) AwaitListening() {
 	t := n.env.t
-	s := safesocket.DefaultConnectionStrategy(n.sockFile)
 	if err := tstest.WaitFor(20*time.Second, func() (err error) {
-		c, err := safesocket.Connect(s)
+		c, err := safesocket.Connect(n.sockFile)
 		if err == nil {
 			c.Close()
 		}