ethereum: fix helper scripts; stop sourcing env files

[bemic]

Summary

EVM deployment, registration, and upgrade helpers previously sourced repository .env files, causing configuration data to execute as shell code in the release operator's process.

This change removes executable env-file loading. Configuration is now supplied
through the operator environment, while devnet reads only the required
registration values from .env as data.

The change also restores the previously unreachable upgrade workflow. The
verifier distinguishes a confirmed bytecode mismatch from operational errors,
new implementations are verified before governance, and generated governance
data is submitted as one quoted argument.

Compatibility

Operators must export the required configuration from a trusted shell, CI
environment, secret manager, or release runner. Files under ethereum/env may
be used as reviewed references but must not be sourced.

Testing

• make test-release-helpers
• make test