Configure CLI arguments from environment variables

[fracek]

I'm using starknet-devnet-rs to test Starknet React V3 and we're hitting an issue with pending blocks and accounts (related to #474). The --blocks-on-demand flag helps with the issue.

We're running devnet as a service in our github actions, but github actions doesn't allow passing additional arguments to the container. I propose to make all cli arguments configurable through environment variables so that they can be used in ci.

[FabijanC]

I'm assigning myself. Seems like it could be as simple as

• expanding the clap features in Cargo.toml with env
• using #[arg(env = VAR_NAME)] on each CLI param in cli.rs.

Note

--cli-params take precedence over ENV_VARS

I.e. ACCOUNTS=0 cargo run -- --accounts 1 would spawn one predeployed account

Would also enable closing of #475.