Update package to use web3.py >=6.0.0, <7

[vile]

This PR aims to support web3.py versions >=6.0.0, <7.

According to the web3.py v6 migration guide, only a few breaking changes apply to this project:

• Use of consistent Pythonic snake_case for method and property names
• renaming the sha3 method to keccak

Outside of the v6 migration guide, there is one other breaking change:

• web3.module.Module renames the web3 property to w3 for the Web3 class (async or sync)

This PR does not add async methods (see: Web3 class split into Web3 and AsyncWeb3).

In addition to the above changes, Poetry packages were locked using the latest web3.py version (6.15.1) and the .vscode/settings.json file was changed to properly format using Black on-save. /example/simple.py has also been updated to use web3.py >=6.0.0.