This PR enables the node_exporter systemd collector and configures the unit whitelist to include scylla-server.service and systemd-coredump services.
**Motivation**: We currently lack visibility into system-level service states, which is critical for diagnosing stability issues.
This configuration enables two specific use cases:
- Detecting Coredump Loops: We encounter scenarios where ScyllaDB enters a restart loop. To pinpoint SIGSEGV (coredumps) as the root cause, we need to track when the systemd-coredump service becomes active, indicating a dump is being processed.
- Identifying Startup Failures: We need to detect when the scylla-server unit enters a failed state. This is essential for catching unrecoverable errors (e.g., corrupted commitlogs or configuration bugs) that prevent the server from starting.
example of promql queries:
- `node_systemd_unit_state{name=~"systemd-coredump@.*", state="active"} == 1`
- `node_systemd_unit_state{name="scylla-server.service", state="failed"} == 1`
Closes#28402
9898e5700b