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/routes/install.go

@@ -9,7 +9,6 @@ import (
 	"net/http"
 	"path"
 
-	"code.gitea.io/gitea/modules/forms"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/public"
 	"code.gitea.io/gitea/modules/setting"
@@ -17,6 +16,7 @@ import (
 	"code.gitea.io/gitea/modules/web"
 	"code.gitea.io/gitea/modules/web/middleware"
 	"code.gitea.io/gitea/routers"
+	"code.gitea.io/gitea/services/forms"
 
 	"gitea.com/go-chi/session"
 )