feat(canary): Support passing arbitrary set of labels to use for the query

[iNoahNothing]

What this PR does / why we need it:
Loki Canary logs are collected and parsed by logging agents whose configuration is controlled by users. Since Loki does not parse logs directly, the set of labels for each log line is up to users and extremely variable.

The current approach only allows for two labels to be used for the query sent to Loki which can impact the canary's ability to find the logs it is looking for. By adding a -labels flag, we are able to pass an arbitrary set of labels to be used in the query. Combined with -query-append, you can craft a full LogQL query to correctly and efficiently return the logs it is looking for.

Checklist

• Reviewed the CONTRIBUTING.md guide (required)
• Documentation added
• Tests updated
• Title matches the required conventional commits format, see here
  • Note that Promtail is considered to be feature complete, and future development for logs collection will be in Grafana Alloy. As such, feat PRs are unlikely to be accepted unless a case can be made for the feature actually being a bug fix to existing behavior.
• Changes that require user attention or interaction to upgrade are documented in docs/sources/setup/upgrade/_index.md
• If the change is deprecating or removing a configuration option, update the deprecated-config.yaml and deleted-config.yaml files respectively in the tools/deprecated-config-checker directory. Example PR

[CLAassistant]

All committers have signed the CLA.

[iNoahNothing]

@MasslessParticle Sorry for the ping but you seem to be the last person whose looked at the canary stuff #14287

Is there anything I can do to get this over the line?

[iNoahNothing]

@paul1r Sorry for the ping. Any chance we can get eyes on this or should I expect to need to fork the project to make this change?