feat(boundary): setup of rate-limit canister

[nikolay-komarevskiy]

How to run e2e canister client tests:

1. Deploy canister: $ rs/boundary_node/rate_limits $ dfx deploy rate_limit_canister --network playground --no-wallet
2. Set canister_id in rs/boundary_node/rate_limits/canister_client/src/main.rs.
3. Run canister client: rs/boundary_node/rate_limits/canister_client $ cargo run