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_generate_access_token.go

@@ -9,27 +9,29 @@ import (
 	auth_model "code.gitea.io/gitea/models/auth"
 	user_model "code.gitea.io/gitea/models/user"
 
-	"github.com/urfave/cli"
+	"github.com/urfave/cli/v2"
 )
 
-var microcmdUserGenerateAccessToken = cli.Command{
+var microcmdUserGenerateAccessToken = &cli.Command{
 	Name:  "generate-access-token",
 	Usage: "Generate an access token for a specific user",
 	Flags: []cli.Flag{
-		cli.StringFlag{
-			Name:  "username,u",
-			Usage: "Username",
+		&cli.StringFlag{
+			Name:    "username",
+			Aliases: []string{"u"},
+			Usage:   "Username",
 		},
-		cli.StringFlag{
-			Name:  "token-name,t",
-			Usage: "Token name",
-			Value: "gitea-admin",
+		&cli.StringFlag{
+			Name:    "token-name",
+			Aliases: []string{"t"},
+			Usage:   "Token name",
+			Value:   "gitea-admin",
 		},
-		cli.BoolFlag{
+		&cli.BoolFlag{
 			Name:  "raw",
 			Usage: "Display only the token value",
 		},
-		cli.StringFlag{
+		&cli.StringFlag{
 			Name:  "scopes",
 			Value: "",
 			Usage: "Comma separated list of scopes to apply to access token",