cleanup: mark more integration tests as !short mode (#755)

The objective is to make PR checks run much faster.

See https://github.com/ooni/probe/issues/2113 for context.

Regarding netxlite's tests:

Checking for every commit on master or on a release branch is
good enough and makes pull requests faster than one minute since
netxlite for windows is now 1m slower than coverage.

We're losing some coverage but coverage from integration tests
is not so good anyway, so I'm not super sad about this loss.

internal/netxlite/filtering/dns_test.go

@@ -16,6 +16,9 @@ import (
 )
 
 func TestDNSProxy(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skip test in short mode")
+	}
 	newProxyWithCache := func(action DNSAction, cache map[string][]string) (DNSListener, <-chan interface{}, error) {
 		p := &DNSProxy{
 			Cache: cache,

internal/netxlite/filtering/http_test.go

@@ -16,6 +16,9 @@ import (
 )
 
 func TestHTTPProxy(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skip test in short mode")
+	}
 	newproxy := func(action HTTPAction) (net.Listener, error) {
 		p := &HTTPProxy{
 			OnIncomingHost: func(host string) HTTPAction {

internal/netxlite/filtering/tls_test.go

@@ -14,6 +14,9 @@ import (
 )
 
 func TestTLSProxy(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skip test in short mode")
+	}
 	newproxy := func(action TLSAction) (net.Listener, <-chan interface{}, error) {
 		p := &TLSProxy{
 			OnIncomingSNI: func(sni string) TLSAction {

internal/netxlite/filtering/tproxy_test.go

@@ -389,6 +389,9 @@ func TestTProxyOnIncomingHost(t *testing.T) {
 }
 
 func TestTProxyDial(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skip test in short mode")
+	}
 	t.Run("with drop SYN", func(t *testing.T) {
 		config := &TProxyConfig{
 			Endpoints: map[string]TProxyPolicy{