Move modules/forms to services/forms (#15305)

Forms are dependent on models and therefore should be in services.

This PR also removes the old auth. aliasing

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

routers/user/setting/account_test.go

@@ -9,10 +9,10 @@ import (
 	"testing"
 
 	"code.gitea.io/gitea/models"
-	auth "code.gitea.io/gitea/modules/forms"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/test"
 	"code.gitea.io/gitea/modules/web"
+	"code.gitea.io/gitea/services/forms"
 
 	"github.com/stretchr/testify/assert"
 )
@@ -86,7 +86,7 @@ func TestChangePassword(t *testing.T) {
 		test.LoadUser(t, ctx, 2)
 		test.LoadRepo(t, ctx, 1)
 
-		web.SetForm(ctx, &auth.ChangePasswordForm{
+		web.SetForm(ctx, &forms.ChangePasswordForm{
 			OldPassword: req.OldPassword,
 			Password:    req.NewPassword,
 			Retype:      req.Retype,