chore: replace testing.Testing with flag lookup (#26552)

In our codebase we have an existing convention of using
`flag.Lookup("test.v")` instead of `testing.Testing()`. This avoids
pulling in the entire `testing` package. Another consequence: some of
our custom linters trigger upon import of the `testing` package which
can lead to unexpected linter errors.

cli/server.go

@@ -30,7 +30,6 @@ import (
 	"strings"
 	"sync"
 	"sync/atomic"
-	"testing"
 	"time"
 
 	"github.com/charmbracelet/lipgloss"
@@ -2400,10 +2399,10 @@ func startBuiltinPostgres(ctx context.Context, cfg config.Root, logger slog.Logg
 	// in CI and cause flaky tests.
 	maxAttempts := 1
 	_, err = cfg.PostgresPort().Read()
-	// Important: if retryPortDiscovery is changed to not include testing.Testing(),
+	// Important: if retryPortDiscovery is changed to not include flag.Lookup("test.v") != nil,
 	// the retry logic below also needs to be updated to ensure we don't delete an
 	// existing database
-	retryPortDiscovery := errors.Is(err, os.ErrNotExist) && testing.Testing()
+	retryPortDiscovery := errors.Is(err, os.ErrNotExist) && flag.Lookup("test.v") != nil
 	if retryPortDiscovery {
 		maxAttempts = 10
 	}