Enable CLI parameter specification via env vars

[FabijanC]

Usage related changes

• Closes Configure CLI arguments from environment variables #482
• Closes Feature request: Add CLI option that loads devnet config from JSON file. #475
• More info in the updated .md documentation files
• Improves #[arg(value_name = ...)] of some CLI parameters.

Development related changes

• Enable the env feature of the clap dependency in Cargo.toml.
• Introduces serial_test dev dependency because env-mainpulating tests cannot be run in parallel.
  • Apparently env::remove_var should be unsafe but isn't.

Checklist:

• Checked out the contribution guidelines
• Applied formatting - ./scripts/format.sh
• No linter errors - ./scripts/clippy_check.sh
• No unused dependencies - ./scripts/check_unused_deps.sh
• No spelling errors - ./scripts/check_spelling.sh
• Performed code self-review
• Rebased to the latest commit of the target branch (or merged it into my branch)
• Updated the docs if needed - ./website/README.md
• Linked the issues resolvable by this PR - linking info
• Updated the tests if needed; all passing - execution info

[marioiordanov]

What will happen if cli args and env variables are passed

[FabijanC]

What will happen if cli args and env variables are passed

I thought I added this info, thanks for reminding me. Updated the docs in e268e43