Traitify Substrate client (#2129)

* layered client implementation: initial commit

* migrate more methods

* fmt

* more methods migration

* runtime_version

* more functions migrated to new client

* moved submit_unsigned_extrinsic

* migrated submit_signed_extrinsic

* moved submit_and_watch_signed_extrinsic

* moved pending_extrinsics

* moved validate_transaction

* moved estimate_extrinsic_weight

* moved state_call

* moved state_call

* moved prove_storage

* migrate ensure_synced

* migrated subscribe_finality_justifications

* use state_call to call runtime API methods

* fix subscriptions usage

* substrate-relay-helper migrated to new client

* migrated substrate-relay

* some small changes

* new (shared) subscriptions

* removed old client + fixed all warnings

* renamed new_client -> client

* started cleanup

* comments + ref issue in TODO

* more docs

* mv relays/client-substrate/src/rpc.rs relays/client-substrate/src/client/rpc_api.rs

* fix TODO

* revive transaction_tracker tests + change underlying type of subscription

* cleanup

* cleanup

* cleanup

* impl review suggestions

* trigger CI

* Revert "trigger CI"

This reverts commit ecd00d38.