feat(frontend): kong_backend integration

[DenysKarmazynDFINITY]

Motivation

This PR includes all the necessary steps for the integration of the kong_backend canister, as well as the services required for the Kong swap functionality. The PR will be later reviewed and merged into main in smaller chunks.

Changes

1. Script for building kong_backend by using the respective WASM and candid files available in the KongSwap repo.
2. Script for deploying kong_backend locally.
3. Script for generating, updating and deleting declaration files (src/declarations/kong_backend/*).
4. Required services (swap, swap_async), types, env vars, and tests to be used later by frontend.
5. Dfx config update with the kong_swap canister.

Tests

Unit tests for kong backend services are included.