Migrate to urfave v3 (#34510)

migrate cli to urfave v3

add more cli tests

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

cmd/mailer.go

@@ -4,24 +4,18 @@
 package cmd
 
 import (
+	"context"
 	"fmt"
 
 	"code.gitea.io/gitea/modules/private"
 	"code.gitea.io/gitea/modules/setting"
 
-	"github.com/urfave/cli/v2"
+	"github.com/urfave/cli/v3"
 )
 
-func runSendMail(c *cli.Context) error {
-	ctx, cancel := installSignals()
-	defer cancel()
-
+func runSendMail(ctx context.Context, c *cli.Command) error {
 	setting.MustInstalled()
 
-	if err := argsSet(c, "title"); err != nil {
-		return err
-	}
-
 	subject := c.String("title")
 	confirmSkiped := c.Bool("force")
 	body := c.String("content")