Allow customizing the process for the entrypoint.sh script

[TrevorBenson]

Description

Implements an ENTRYPOINT_PROCES.

• When undefined cnode.sh is the ENTRYPOINT_PROCESS persisting the current behavior of the cardano-node container.
• When defined the process exec'd at the end is a script inside the "${CNODE_HOME}/scripts/${ENTRYPOINT_PROCESS}" "$@".

Motivation and context

This allows a simple method to change the containers startup script dynamically while persisting the configuration files copied in place by the NETWORK environment variable

Which feature request it closes?

closes #1797

How has this been tested?

loaded and running cardano-node, mithril-signer and cncli.sh containers with a test image on ghcr.io. Using quadlet / podman systemd (man podman-systemd.unit) to run multiple containers and pass in the ENTRYPOINT_PROCESS when needed.

# grep -e ENTRYPOINT_PROCESS -e Exec /etc/containers/systemd/preprod-*.container
/etc/containers/systemd/preprod-cncli-leaderlog.container:Environment="ENTRYPOINT_PROCESS=cncli.sh"
/etc/containers/systemd/preprod-cncli-leaderlog.container:Exec="leaderlog"
/etc/containers/systemd/preprod-cncli-sync.container:Environment="ENTRYPOINT_PROCESS=cncli.sh"
/etc/containers/systemd/preprod-cncli-sync.container:Exec="sync"
/etc/containers/systemd/preprod-cncli-validate.container:Environment="ENTRYPOINT_PROCESS=cncli.sh"
/etc/containers/systemd/preprod-cncli-validate.container:Exec="validate"
/etc/containers/systemd/preprod-mithril-signer.container:Environment="ENTRYPOINT_PROCESS=mithril-signer.sh"
/etc/containers/systemd/preprod-mithril-signer.container:Exec="-D"
# systemctl is-active preprod-{cncli-{sync,leaderlog,validate},mithril-signer}
active
active
active
active
# podman ps | awk '/preprod/ {print $2, $NF}'
ghcr.io/trevorbenson/cardano-node:multi-process preprod-pool-ccio
ghcr.io/trevorbenson/cardano-node:multi-process preprod-cncli-sync
ghcr.io/trevorbenson/cardano-node:multi-process preprod-cncli-leaderlog
ghcr.io/trevorbenson/cardano-node:multi-process preprod-cncli-validate
ghcr.io/trevorbenson/cardano-node:multi-process preprod-mithril-signer