Switch to new RPC interface (#131)

* Move EthereumRpc implementation to Eth client

* Move SubstrateRpc implementation to SubstrateClient

* Update deploy_contract to use new RPC interface

* Fix some types in the Substrate client

* Swap out method bodies in Eth sync loop

* Swap out method bodies in Substrate sync loop

* Remove Client from SourceClient trait return types

* Remove Client from TargetClient trait return types

* Remove client from Source select! arms

* Remove client from Target select! arms

* Add missing mutable refs in Substrate client

* Use mutable references in Source/Target Client traits

* Try and use mutable references in Source/Client trait implementations

* Handle errors more gracefully

* Remove unused imports

* Remove dead_code and unused_variables lints

* Remove usage of `jsonrpsee::RawClient`

By using a `jsonrpsee::Client` we are able to remove all the shared
mutable references required when interacting with the RPC server. This
is convenient as trying to sharing mutable references in code that uses
async/await is a bit of a pain.

However, using a `Client` instead of a `RawClient` is not yet supported
by the `jsonrpsee::rpc_api` macro, so a fork must be used for the moment.

* Clean up dead code and warnings

* Clean up higher level RPCs

Some of the RPCs that were "high level" didn't necessarily belong
as part of the trait, so they were removed.

* Use positional parameters for RPCs

Both Substrate and Ethereum's RPCs use positional (array) parameters,
so in order to be compatible with both we need to make sure that
our API is defined with positional paramters in mind.

* Rename argument for eth_getBlockByNumber

* Remove some unecessary Ok-wraps

* Process client requests synchonously

Before the refactoring the sync loop would wait until a client finished
handling a request before issuing another one. This behaviour was
inadvertently changed during the refactoring leading to race conditions.
This commit makes sure that the previous behaviour is respected.

* Reduce the errors that are considered a connection error

* Only decode bridge contract once

* Set genesis_config at RPC client startup

* Fetch genesis hash in SubstrateRpcClient::new()

* Move Decode error into SubstrateNodeError

* Suppress warnings caused by `rpc_api!`

* Implement From RpcError for String

* Handle Substrate client initalization errors more gracefully

* Remove match in favour of ?

Co-authored-by: Svyatoslav Nikolsky <[email protected]>