Add support for config file

[hegjon]

I have made RPM package for MEV-Boost that is hosted currently at https://copr.fedorainfracloud.org/coprs/jonny/Ethereum/

The source for the SPEC files used to build the RPM can be found here:
https://github.com/hegjon/mev-boost-rpm

The biggest issue is that the configuration and the systemd unit file is in the same file, making it more harder for administrators to change the config. It would be great to be able to ship a systemd unit file that allows updating the package to also reload the service, while keeping the configuration unchanged.

I have tried to make it better by loading the arguments from EnvironmentFile, but I feel it is only a hack for now:

mev-boost@.service

EnvironmentFile=/etc/mev-boost/%i.conf
ExecStart=/usr/bin/mev-boost $MEV_BOOST_ARGS

And the environment file for mainnet:

MEV_BOOST_ARGS=" \
 -mainnet
 -relay-check \
 -relay YOUR_RELAY_CHOICE_A \
 -relay YOUR_RELAY_CHOICE_B \
 -relay YOUR_RELAY_CHOICE_C \
"

[hegjon]

#352 will also run into this issue, it would be great if the setup was the same for both setups

[ralexstokes]

@hegjon I'll note that I have written mev-boost-rs (repo: https://github.com/ralexstokes/mev-rs, docs: https://mev-rs.pbs.dev/mev-boost-rs.html) so that it takes a single config file as the source of configuration, rather than a laundry list of command line args

the big caveat here is that mev-boost has seen a lot more production usage although I run mev-boost-rs in many of my testnet setups and haven't had any issue to date. you could try running mev-boost-rs in your testnet/staging environments and if you gain confidence then try mainnet

also happy to provide support if you run into any issues along the way