Skip initing disabled storages (#21985)

If `Attachment` or `Packages` are disabled, we don't have to init the
storages for them.

modules/storage/helper.go

@@ -4,6 +4,10 @@
 package storage
 
 import (
+	"fmt"
+	"io"
+	"net/url"
+	"os"
 	"reflect"
 
 	"code.gitea.io/gitea/modules/json"
@@ -61,3 +65,31 @@ func toConfig(exemplar, cfg interface{}) (interface{}, error) {
 	}
 	return newVal.Elem().Interface(), nil
 }
+
+var uninitializedStorage = discardStorage("uninitialized storage")
+
+type discardStorage string
+
+func (s discardStorage) Open(_ string) (Object, error) {
+	return nil, fmt.Errorf("%s", s)
+}
+
+func (s discardStorage) Save(_ string, _ io.Reader, _ int64) (int64, error) {
+	return 0, fmt.Errorf("%s", s)
+}
+
+func (s discardStorage) Stat(_ string) (os.FileInfo, error) {
+	return nil, fmt.Errorf("%s", s)
+}
+
+func (s discardStorage) Delete(_ string) error {
+	return fmt.Errorf("%s", s)
+}
+
+func (s discardStorage) URL(_, _ string) (*url.URL, error) {
+	return nil, fmt.Errorf("%s", s)
+}
+
+func (s discardStorage) IterateObjects(_ func(string, Object) error) error {
+	return fmt.Errorf("%s", s)
+}