Context
The RPC class used to manipulate the state of the local network/take snapshots during the unit/integration tests relies on the web3 library - which is passed down its constructor upon initialization.

TODO

• replace web3.js methods with ethers.js as a dependency in the RPC class
• replace web3.js with ethers.js in all the occurrences where the RPC class is being initialized. Additionally, remove web3.js from the imports if it's not being used for anything else

Related to #566