Refactor reward account handling to use StakeAddress

[lowhung]

Description of Changes

• Replaced RewardAccount with StakeAddress across modules for consistency.
• Updated serialization, deserialization, and encoding/decoding logic to align with StakeAddress.
• Adjusted tests, helpers, and corresponding comments to support the refactor.

[Copilot]

Pull Request Overview

This PR refactors the codebase to replace the RewardAccount type (which was a Vec<u8>) with the more structured StakeAddress type for improved type safety and consistency across the application.

Key Changes:

• Replaced RewardAccount type alias with StakeAddress throughout the codebase
• Updated serialization/deserialization logic to use StakeAddress methods
• Modified test fixtures to use StakeAddress::default() instead of empty vectors

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
modules/tx_unpacker/src/map_parameters.rs	Updated certificate and proposal mapping to deserialize reward accounts using StakeAddress::from_binary()
modules/spo_state/src/state.rs	Updated test fixtures to use StakeAddress::default() instead of vec![0] and added import
modules/rest_blockfrost/src/handlers/pools.rs	Changed reward account conversion from to_bech32_with_hrp() to to_string() method
modules/accounts_state/src/verifier.rs	Updated verifier to use StakeAddress::get_hash() for comparisons and logging
modules/accounts_state/src/state.rs	Refactored SPO retirement logic to use StakeAddress directly, updated reward processing to use get_hash(), and fixed comment grammar
modules/accounts_state/src/snapshot.rs	Simplified reward account registration check by removing error handling and using StakeAddress directly
modules/accounts_state/src/rewards.rs	Updated reward calculation to work with StakeAddress, replaced hash comparisons with get_hash() calls
common/src/types.rs	Removed RewardAccount type alias and updated PoolRegistration and ProposalProcedure to use StakeAddress
common/src/address.rs	Added CBOR encoding/decoding implementations, Default trait, reorganized methods, and added comprehensive tests for StakeAddress

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