🛠️ [TASK] : Public and Private vote tx v2 decoding implementation

[Mr-Leshiy]

Summary

Add a CBOR decoding and encoding implementation according to the https://input-output-hk.github.io/catalyst-libs/architecture/08_concepts/catalyst_voting/v2/ spec for public and private vote transactions

Description

• Add a new structs like PublicVoteTx and PrivateVoteTx into the vote-tx-v2 crate.
• Based on the vote_tx_v2_public.cddl and vote_tx_v2_private.cddl specs implement a CBOR decoding/encoding functionality for these types.

[stevenj]

Issue is temporarily parked due to a change in priorities.