refactor: introducing hyperswitch_interface crates

[Chethan-rao]

Type of Change

• Bugfix
• New feature
• Enhancement
• Refactoring
• Dependency updates
• Documentation
• CI/CD

Description

Create a new crate Hyperswitch-interface containing below modules for now:
secrets_interface: Module used for application config encryption and decryption during startup which will contain its own trait and error types
encryption_interface: Module used for user value encryption and decryption during runtime which will contain its own trait and error types

This PR only adds the above crate with the addition of secret_management_config and encryption_management_config in the router

Additional Changes

• This PR modifies the API contract
• This PR modifies the database schema
• This PR modifies application configuration/environment variables

Motivation and Context

How did you test it?

New crates addition which doesn't integrate with other existing crates yet. So basic sanity testing should suffice

Checklist

• I formatted the code cargo +nightly fmt --all
• I addressed lints thrown by cargo clippy
• I reviewed the submitted code
• I added unit tests for my changes where possible
• I added a CHANGELOG entry if applicable