Docs: Clarify "supported data sources" (#54337) (#55642)

* Docs: Clarify "supported data sources"

The term "supported" is context-dependent. Clarify the data sources
index page to link to the plugins catalog with additional detail,
and specify that the links to data sources are for those with
additional documentation content as part of Grafana.

Add a link to the tutorial to build a data source plugin.

* Update docs/sources/datasources/_index.md

Co-authored-by: Fiona Artiaga <89225282+GrafanaWriter@users.noreply.github.com>

Co-authored-by: Fiona Artiaga <89225282+GrafanaWriter@users.noreply.github.com>
(cherry picked from commit f0e3b9b)

Co-authored-by: Garrett Guillotte <100453168+gguillotte-grafana@users.noreply.github.com>

docs/sources/datasources/_index.md

@@ -16,7 +16,9 @@ Each data source has a specific Query Editor that is customized for the features
 
 ## Supported data sources
 
-The following data sources are officially supported:
+> **Note:** For a list of all data source plugins created by Grafana Labs, view the [plugin catalog](https://grafana.com/grafana/plugins/?type=datasource) and select the "Data sources" and "Grafana Labs created" filters. For a list of all Enterprise-level plugins, which have additional support, also enable the [Enterprise filter](https://grafana.com/grafana/plugins/?enterprise=1&type=datasource).
+
+These data sources have additional documentation:
 
 - [Alertmanager]({{< relref "./alertmanager/" >}})
 - [AWS CloudWatch]({{< relref "./aws-cloudwatch/" >}})
@@ -36,7 +38,7 @@ The following data sources are officially supported:
 - [Tempo]({{< relref "./tempo/" >}})
 - [Testdata]({{< relref "./testdata/" >}})
 
-In addition to the data sources that you have configured in your Grafana, there are three special data sources available:
+In addition to the data sources that you have configured in your Grafana instance, there are three special data sources available:
 
 - **Grafana -** A built-in data source that generates random walk data. Useful for testing visualizations and running experiments.
 - **Mixed -** Select this to query multiple data sources in the same panel. When this data source is selected, Grafana allows you to select a data source for every new query that you add.
@@ -47,4 +49,4 @@ In addition to the data sources that you have configured in your Grafana, there
 
 ## Data source plugins
 
-Since Grafana 3.0 you can install data sources as plugins. Check out [Grafana.com/plugins](https://grafana.com/plugins) for more data sources.
+You can install additional data sources as plugins. To view available data source plugins, see the [Grafana Plugins catalog](https://grafana.com/plugins). To build your own, see the ["Build a data source plugin"](https://grafana.com/tutorials/build-a-data-source-plugin/) tutorial and our documentation about [building a plugin](/developers/plugins/).