Meta: Rust crates

[xlc]

Rust crates that will be implemented in this repo

• pvq-executor
  • An executor that's able to execute PVQ program
• pvq-api
  • Interface for PVQ program
• pvq-extension
  • The PVQ extension system
• pvq-extension-core
  • The implementation of the Core extension
• pvq-extension-fungibles
  • The implementation of the Fungibles extension
• pvq-runtime-api
  • Defines the XCQ Runtime API
• pvq-test-runner
  • A test runner that's able to run PVQ program with mock data
• examples
  • A list of PVQ program examples