Add logs enrich

[v-zhuravlev]

Background

Logs and metrics correlation is very powerful concept that easy to achieve in Grafana with alloy, if logs/metrics are collected with the same agent.

However, it is not always the case:

• For network devices logs can be received via syslog protocol or other push protocol, while metrics could be collected with snmp_exporter.

Proposal

To make sure that logs/metrics correlation is possible even with logs pushed without any additional metadata/labels, I would like to propose a component similar to https://www.rsyslog.com/doc/configuration/lookup_tables.html but instead of files, powerful prometheus discovery components can be used, since good probability that those could also be used for snmp metrics collection as well.

Examples:

1)Enrich Network devices syslog messages with device metadata(as labels) from IP address management (IPAM)/Data center infrastructure management(DCIM) like Netbox (https://github.com/FlxPeters/netbox-plugin-prometheus-sd). It could be same labels as used by prometheus.exporter.snmp or other metric scrapers.
2) Ensure metrics and logs use same labelset (gathered from same discovery.* component) even if metrics are scraped from prometheus endpoints and logs are received via loki.source.api.

Going forward, i created a component loki.enrich that could just do exactly that:
PR,

However there is also function array.combine_maps that does something similar, but, unfotrunately not working for logs scenarios describred right now.