Unify error enums in substrate and ethereum clients with thiserror

[vmarkushin]

Related to #857

[tomusdrw]

The changes in the current draft look good, but I was hoping we can get rid of all of the String error types and replace them with anyhow or concrete instances.

[vmarkushin]

The changes in the current draft look good, but I was hoping we can get rid of all of the String error types and replace them with anyhow or concrete instances.

Yeah, I wasn't certain about all the String errors. Now it's clear, I will deal with the rest.

[tomusdrw]

@vmarkushin any updates on this? I'm okay merging this as-is and leaving the String error types eradication for future PRs.

[vmarkushin]

@tomusdrw I worked on the code a bit more. Please check it when you have time.

[tomusdrw]

Looks great, thanks a lot! License pre-amble is missing in new files, but apart from that I'm happy to get that merged.

[tomusdrw]

Suggested change

	use thiserror::Error;
	// Copyright 2021 Parity Technologies (UK) Ltd.
	// This file is part of Parity Bridges Common.
	// Parity Bridges Common is free software: you can redistribute it and/or modify
	// it under the terms of the GNU General Public License as published by
	// the Free Software Foundation, either version 3 of the License, or
	// (at your option) any later version.
	// Parity Bridges Common is distributed in the hope that it will be useful,
	// but WITHOUT ANY WARRANTY; without even the implied warranty of
	// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	// GNU General Public License for more details.
	// You should have received a copy of the GNU General Public License
	// along with Parity Bridges Common. If not, see <http://www.gnu.org/licenses/>.
	use thiserror::Error;

[tomusdrw]

Suggested change

	use std::net::AddrParseError;
	// Copyright 2019-2021 Parity Technologies (UK) Ltd.
	// This file is part of Parity Bridges Common.
	// Parity Bridges Common is free software: you can redistribute it and/or modify
	// it under the terms of the GNU General Public License as published by
	// the Free Software Foundation, either version 3 of the License, or
	// (at your option) any later version.
	// Parity Bridges Common is distributed in the hope that it will be useful,
	// but WITHOUT ANY WARRANTY; without even the implied warranty of
	// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	// GNU General Public License for more details.
	// You should have received a copy of the GNU General Public License
	// along with Parity Bridges Common. If not, see <http://www.gnu.org/licenses/>.
	use std::net::AddrParseError;

[tomusdrw]

Thanks!!!