CfgEnv.chain_id should be u64

[thedevbirb]

Closes #671. Let me know if I am missing something from this issue!

[DaniPopes]

hm actually i realized this is wrong, realistically chain id is a u64 but users should be able to set any arbitrary u256 in the EVM

[rakita]

hm actually i realized this is wrong, realistically chain id is a u64 but users should be able to set any arbitrary u256 in the EVM

This is one of those ambiguous things where the upper limit was not specified but all the "chains" use u64, so it is a good call to use u64.

Here is a site that lists chain ids: https://chainlist.org/
from github list is here: https://github.com/DefiLlama/chainlist/blob/main/constants/chainIds.json
And biggest value is: 836542336838601

[rakita]

lgtm

[DaniPopes]

Makes sense, this is also enforced in Foundry:

https://github.com/foundry-rs/foundry/blob/675a824648b6259c1566009b79356a4fc109b6ac/crates/evm/src/executor/inspector/cheatcodes/env.rs#L548-L552