* packaging updates
* one package per binary (nimbus_beacon_node, nimbus_validator_client)
* use `-` in package name (`_` is separating the version)
* don't include (un)installation scripts in package
* default metrics port 8108 for vc
* fix several upgrade/install errors in scripts
* add JWT option to service files
* don't attempt to remove user on purge
* RPM/DEB for systemd-based systems
Similar to https://github.com/status-im/nimbus-eth2/pull/2691, this PR
introduces packaging for nimbus beacon node.
Instead of relying on interactive prompts, a default configuration is
included that connects to mainnet and expects there to be an execution
client running with websockets enabled on the same host, on the standard
websocket port.
Should the user need to configure their nimbus after installation (for
example with a different web3 url), the "standard" way of doing so via
`systemctl` edit is recommended.
Jacek Sieka