Docs: Add queries.md (#24363)

* Create queries.md

* Delete mixed.md

* Update _index.md

* Update menu.yaml

* Update queries.md

* Update menu.yaml

* Update queries.md

* Update queries.md

* Update queries.md

* Update docs/sources/panels/queries.md

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>

* Update docs/sources/panels/queries.md

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>

* Update docs/sources/panels/queries.md

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>

* Update queries.md

* Update queries.md

* Update queries.md

* Update queries.md

* Update queries.md

* Update queries.md

Co-authored-by: Dominik Prokop <dominik.prokop@grafana.com>

docs/sources/features/datasources/_index.md

@@ -29,7 +29,6 @@ The following data sources are officially supported:
 * [InfluxDB]({{< relref "influxdb.md" >}})
 * [Loki]({{< relref "loki.md" >}})
 * [Microsoft SQL Server (MSSQL)]({{< relref "mssql.md" >}})
-* [Mixed]({{< relref "mixed.md" >}})
 * [MySQL]({{< relref "mysql.md" >}})
 * [OpenTSDB]({{< relref "opentsdb.md" >}})
 * [PostgreSQL]({{< relref "postgres.md" >}})

docs/sources/features/datasources/mixed.md

@@ -1,19 +0,0 @@
-+++
-title = "Using the Mixed Data Source in Grafana"
-keywords = ["grafana", "dashboard", "documentation", "panels", "mixeddata"]
-type = "docs"
-[menu.docs]
-name = "MixedData"
-parent = "datasources"
-weight = 20
-+++
-
-# Mixed Data Source
-
-This Data Source allows you to specify data source on a per query basis.
-
-## Usage
-
-To use the Mixed Data Source, create a new panel or edit an existing panel and navigate to the Queries tab. From the Query popup, select "-- Mixed --". Click "Add Query" and select the desired source.
-
-You cannot change an existing query to use the Mixed Data Source.