fix: misc fixes in pub/gpg/tests (#38809)

- The pub registry reported the oldest version as `latest`, because the
descriptor slice is sorted ascending but the first element was used.
- Verifying a GPG or SSH key flashed success and redirected after
already writing an error response, so a failure was reported as a
success with an empty key id.
- Test packages sharing redis could tear down each other's server.
`PrepareTestRedis` started its own on the well-known port, so a package
running in parallel borrowed it and lost it when the owner's cleanup
fired. It now listens on a socket of its own.

modules/globallock/globallock_test.go

@@ -7,6 +7,9 @@ import (
 	"context"
 	"sync"
 	"testing"
+	"time"
+
+	"gitea.dev/modules/test"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -14,6 +17,7 @@ import (
 
 func TestLockAndDo(t *testing.T) {
 	t.Run("redis", func(t *testing.T) {
+		defer test.MockVariableValue(&redisLockExpiry, 5*time.Second)() // Close waits for the extend goroutine's next tick
 		locker := newTestRedisLocker(t)
 		defaultLocker.Store(new(locker))
 		testLockAndDo(t)