Display pflag.CommandLine flags as if they were declared on the parent

```go
package main

import (
	"github.com/spf13/cobra"
	"github.com/spf13/pflag"
)

func main() {
	cmd := &cobra.Command{
		Use:   "min",
		Short: "minimal command",
		Run:   func(_ *cobra.Command, _ []string) {},
	}

	pflag.String("oncmdline", "oncmdline", "oncmdline")
	cmd.Execute()
}
```

Is a minimal cobra program.  When --help is displayed without this patch
you only get:

But with the patch --oncmdline is shows under flags.

cobra_test.go

@@ -963,3 +963,11 @@ func TestGlobalNormFuncPropagation(t *testing.T) {
 		t.Error("cmdPrint and cmdEchoSub should had the normalization function of rootCmd")
 	}
 }
+
+func TestFlagOnPflagCommandLine(t *testing.T) {
+	flagName := "flagOnCommandLine"
+	pflag.CommandLine.String(flagName, "", "about my flag")
+	r := fullSetupTest("--help")
+
+	checkResultContains(t, r, flagName)
+}