chore(sidecar): review default options for CLI flags

[thedevbirb]

There are many configuration options in the sidecar that have a default (for testing reasons) but they shouldn't have one, and we should make sure the users manually sets them. Some examples include:

• fee recipient
• builder private key
• jwt hex
• etc..

This requires also modifying our fork of the Ethereum package in order to provide the correct values and run the devnet successfully.

A PR should be built on top of #296 which already touches some of the CLI flag descriptions etc.