Is your feature request related to a problem? Please describe.

EC of split objects should be properly supported. Once small objects are fine, we're ready for big deal

Describe the solution you'd like

following parts should be updated to support two-level header nesting:

• neofs-node/pkg/core/object/fmt.go

  Line 137 in dab0436

  func (v *FormatValidator) Validate(obj *object.Object, unprepared bool) error {

• object GET
• GC

maybe there is something else, it will become clearer in progress