all: Use context in lib/dialer (#6177)

* all: Use context in lib/dialer

* a bit slimmer

* https://github.com/syncthing/syncthing/pull/5753

* bot

* missed adding debug.go

* errors.Cause

* simultaneous dialing

* anti-leak

lib/ur/usage_report.go

@@ -373,8 +373,8 @@ func (s *Service) sendUsageReport() error {
 
 	client := &http.Client{
 		Transport: &http.Transport{
-			Dial:  dialer.Dial,
-			Proxy: http.ProxyFromEnvironment,
+			DialContext: dialer.DialContext,
+			Proxy:       http.ProxyFromEnvironment,
 			TLSClientConfig: &tls.Config{
 				InsecureSkipVerify: s.cfg.Options().URPostInsecurely,
 			},