feat: Add estimate_gas and get_gas_price calls

[zvolin]

No description provided.

[roberts-pumpurs]

Mostly lgtm. Added some comments for provoking some thoughts/spawning discussions, but none are really actionable. Approving because I won't have the time for another review today

[roberts-pumpurs]

I am not entirely convinced by the general architecture that your ethereum-canister would need to expose and proxy different contract methods (e.g erc20 balanceOf, ownerOf, etc). Because this means that are putting on the mantel of supporting all the different ERCs that are going to come out.
A much more scalable approach imo would be just to expose generic "query" and simulator methods, and then there can be a specific etherc20-canister that proxies individual exact calls with .did nice interface. This also would allow the community to build the wrappers for whichever contract they want to interact with. Most fun projects out there in the wild are not generic erc20/erc721 contracts. But that's just food for thought 😄

[oblique]

I am not entirely convinced by the general architecture that your ethereum-canister would need to expose and proxy different contract methods (e.g erc20 balanceOf, ownerOf, etc).
....
A much more scalable approach imo would be just to expose generic "query"

This is a requirement, but we may expose a raw call API.