Add docs for ES|QL Query Log

[luigidellaquila]

Adding documentation for ES|QL Query Log, similar to Search Slow Log.

[luigidellaquila]

This will need to be updated when we have the Beats connector and stack monitoring enabled.

[github-actions]

🔍 Preview links for changed docs

• explore-analyze/query-filter/languages/esql-query-log.md

[leemthompo]

👋 @luigidellaquila do you think this content fits better here or in the ESQL reference? I'm leaning towards the latter...

FYI I think we should probably move the Query multiple sources and Task management sections into the reference eventually too, I'll try to get that done this sprint

[luigidellaquila]

@leemthompo I put it together with Task Management because they look someway related to each other, but I agree that ES|QL Reference could be a better place for both.
Do you want me to move them or should we just merge this and then do the refactoring later?

[leemthompo]

@luigidellaquila let's not merge this here in that case because it will complicate things for redirects

1. I'd recreate these changes in the Elasticsearch repo, adding this page under a new Troubleshooting section
2. We can then move Task management under there in a separate follow up

[luigidellaquila]

Thanks @leemthompo, I'm closing this one in favor of elastic/elasticsearch#131287