Set config as global, update cache, refactor, add core

[kchojn]

• bump web3 version
• add core module
• move EthTxConfig to core and use BaseSettings
• Refactor ethtx.py
• lru_cahce size from config

[piotr-rudnik]

So, global object for settings is not a good idea, but there is little we can do without changing more time, so it's ok. But I'm not sure about changing to pydantic settings model now, it's just by multiple people and everyone would need to upgrade their code to make it work with this. My proposition is to separate my pydantic settings model to another pull request, and merge it with another major version bump.

[kchojn]

You are right, major changes, will do it in 0.4.0 version