Feat: Implement a zero copy requests queue

[GabrielePicco]

This pull request introduces significant changes to enhance the functionality, efficiency, and maintainability of the codebase. Key updates include improvements to queue management, serialization/deserialization, and error handling, along with dependency updates and new utility functions.

Queue Management Enhancements:

• Replaced dynamic HashMap-based QueueAccount with a fixed-size Queue structure, adding constraints for maximum items, arguments, and accounts. Introduced helper methods for item addition, removal, iteration, and lookup.
• Added validation for queue index bounds in process_delegate_oracle_queue to ensure security.

Serialization and Deserialization Improvements:

• Use bytemuck for Queue serialization/deserialization

Error Handling Enhancements:

• Expanded EphemeralVrfError enum with detailed error variants, such as QueueFull, InvalidQueueIndex, and OracleNotAuthorized, to improve error reporting.

Dependency Updates:

• Updated curve25519-dalek to disable default features and incremented steel to version 4.0.2. Added base64 as a new dependency. [1] [2] [3]

New Utility Functions:

• Added is_empty_or_zeroed function to check if an account is empty or zeroed, improving account initialization checks.
• Enhanced initialize_oracle_queue to return a vector of instructions for chunked initialization, accommodating large queue sizes.

[Copilot]

Pull Request Overview

This pull request implements a zero-copy requests queue system to enhance performance and efficiency. The key change replaces the dynamic HashMap-based QueueAccount with a fixed-size Queue structure using zero-copy serialization for improved performance and memory efficiency.

Key changes include:

• Complete refactoring of queue data structure from dynamic HashMap to fixed-size array with bitmap tracking
• Enhanced VRF cryptographic security with proper domain separation and HKDF nonce generation
• Improved error handling with expanded error variants for better debugging

Reviewed Changes

Copilot reviewed 28 out of 29 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
api/src/state/queue.rs	Complete rewrite implementing zero-copy Queue with fixed-size arrays and bitmap tracking
vrf/src/vrf.rs	Enhanced VRF security with HKDF nonce generation and proper domain separation
program/src/request_randomness.rs	Updated to use new Queue structure and added cost transfer mechanism
program/src/provide_randomness.rs	Refactored for new Queue API and added fee collection
program/src/initialize_oracle_queue.rs	Enhanced with chunked initialization support for large queues