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>

safesocket/safesocket_js.go

@@ -15,6 +15,6 @@ func listen(path string) (net.Listener, error) {
 	return memconn.Listen("memu", memName)
 }
 
-func connect(_ *ConnectionStrategy) (net.Conn, error) {
+func connect(_ string) (net.Conn, error) {
 	return memconn.Dial("memu", memName)
 }