Rename the coins folder to networks (#583)

* Rename the coins folder to networks

Ethereum isn't a coin. It's a network.

Resolves #357.

* More renames of coins -> networks in orchestration

* Correct paths in tests/

* cargo fmt

networks/ethereum/README.md

@@ -0,0 +1,15 @@
+# Ethereum
+
+This package contains Ethereum-related functionality, specifically deploying and
+interacting with Serai contracts.
+
+While `monero-serai` and `bitcoin-serai` are general purpose libraries,
+`ethereum-serai` is Serai specific. If any of the utilities are generally
+desired, please fork and maintain your own copy to ensure the desired
+functionality is preserved, or open an issue to request we make this library
+general purpose.
+
+### Dependencies
+
+- solc
+- [Foundry](https://github.com/foundry-rs/foundry)