Add Erigon support for devnets

[Raneet10]

Description

This PR adds support for running erigon client in a remote PoS devnet, including as a validator (feature to run public node is yet to be enabled). Note the express-cli commands/tests are yet to be updated.

Changes

• Bugfix (non-breaking change that solves an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)
• New test case for remote devnet

Breaking changes

Some config variables are added and/or are removed from the .env.

Checklist

• I have added at least 2 reviewer or the whole pos-v1 team
• I have added sufficient documentation in code
• I will be resolving comments - if any - by pushing each fix in a separate commit and linking the commit hash in the comment reply

Testing

• I have tested this code manually on local environment
• I have tested this code manually on remote devnet using express-cli
• I have tested this code manually on mumbai