Refactor to use urfave/cli/v2 (#25959)

Replace #10912

And there are many new tests to cover the CLI behavior

There were some concerns about the "option order in hook scripts"
(https://github.com/go-gitea/gitea/pull/10912#issuecomment-1137543314),
it's not a problem now. Because the hook script uses `/gitea hook
--config=/app.ini pre-receive` format. The "config" is a global option,
it can appear anywhere.

----

## ⚠️ BREAKING ⚠️

This PR does it best to avoid breaking anything. The major changes are:

* `gitea` itself won't accept web's options: `--install-port` / `--pid`
/ `--port` / `--quiet` / `--verbose` .... They are `web` sub-command's
options.
    * Use `./gitea web --pid ....` instead
* `./gitea` can still run the `web` sub-command as shorthand, with
default options
* The sub-command's options must follow the sub-command
* Before: `./gitea --sub-opt subcmd` might equal to `./gitea subcmd
--sub-opt` (well, might not ...)
    * After: only `./gitea subcmd --sub-opt` could be used
    * The global options like `--config` are not affected

cmd/admin_user_delete.go

@@ -11,26 +11,28 @@ import (
 	"code.gitea.io/gitea/modules/storage"
 	user_service "code.gitea.io/gitea/services/user"
 
-	"github.com/urfave/cli"
+	"github.com/urfave/cli/v2"
 )
 
-var microcmdUserDelete = cli.Command{
+var microcmdUserDelete = &cli.Command{
 	Name:  "delete",
 	Usage: "Delete specific user by id, name or email",
 	Flags: []cli.Flag{
-		cli.Int64Flag{
+		&cli.Int64Flag{
 			Name:  "id",
 			Usage: "ID of user of the user to delete",
 		},
-		cli.StringFlag{
-			Name:  "username,u",
-			Usage: "Username of the user to delete",
+		&cli.StringFlag{
+			Name:    "username",
+			Aliases: []string{"u"},
+			Usage:   "Username of the user to delete",
 		},
-		cli.StringFlag{
-			Name:  "email,e",
-			Usage: "Email of the user to delete",
+		&cli.StringFlag{
+			Name:    "email",
+			Aliases: []string{"e"},
+			Usage:   "Email of the user to delete",
 		},
-		cli.BoolFlag{
+		&cli.BoolFlag{
 			Name:  "purge",
 			Usage: "Purge user, all their repositories, organizations and comments",
 		},