Use cci build context. Remove unneeded options from eip712.

[charlielye]

Description

We've moved common environment variables to a cii build context that can be reused across repos.
This also removes a some unused options from the eip712 code in ethereum.js

Checklist:

• I have reviewed my diff in github, line by line.
• Every change is related to the PR description.
• I have linked this pull request to the issue(s) that it resolves.
• There are no unexpected formatting changes, superfluous debug logs, or commented-out code.
• The branch has been rebased against the head of its merge target.
• I'm happy for the PR to be merged at the reviewer's next convenience.