Switch node side to v2 candidate receipts (#5679)
on top of https://github.com/paritytech/polkadot-sdk/pull/5423 This PR implements the plumbing work required for https://github.com/paritytech/polkadot-sdk/issues/5047 . I also added additional helper methods gated by feature "test" in primitives. TODO: - [x] PRDoc --------- Signed-off-by: Andrei Sandu <[email protected]> Co-authored-by: GitHub Action <[email protected]>