Typed dict for transaction dicts

[pacrob]

What was wrong?

Transaction Dicts could use better typing, especially to play better with web3.py

How was it fixed?

This is a test PR (at least to start), copying the TxParams typed dict and any needed sub-types over from web3. If it makes sense, next step will be to pull those types into eth-typing to be shared across both eth-account and web3.

Todo:

• [ ] Clean up commit history
• [ ] Add or update documentation related to these changes
• [ ] Add entry to the release notes

Cute Animal Picture

[pacrob]

This will be a significant change and need to be coordinated with possible changes to web3 - moving types to be used by both to eth-typing or similar. Saving for a web3 v8 activity.