* Regenerate protobufs as frostfs-api introduced `parent_split_id` and
`parent_split_index` fields.
* Fix marshaller and converter for EC header.
* Extend v2 type `ECHeader` with `ParentSplitID` and `ParentSplitIndex` fields.
* Fix message_test for `Object`. Also generate EC headers and check it.
Signed-off-by: Airat Arifullin <a.arifullin@yadro.com>