Docs: Add Grafana basics section (#32693)

* moved files

* single sourcing

* Update _index.md

* Update heatmap.md

* Update _index.md

* Update _index.md

* Fixed 7 broken relrefs

* Fixed one more broken relref.

Co-authored-by: achatterjee-grafana <aparajita.chatterjee@grafana.com>

docs/sources/shared/basics/grafana-cloud.md

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+---
+title: Grafana Cloud
+---
+
+## Grafana Cloud
+
+Grafana Cloud is a highly available, fast, fully managed OpenSaaS logging and metrics platform. Everything you love about Grafana, but Grafana Labs hosts it for you and handles all the headaches.
+
+[Learn more about Grafana Cloud](https://grafana.com/cloud/) or try the [Grafana Cloud Linux host quickstart](/docs/grafana-cloud/quickstart/).

docs/sources/shared/basics/grafana-enterprise.md

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+---
+title: Grafana Enterprise
+---
+
+## Grafana Enterprise
+
+[Grafana Enterprise]({{< relref "../../enterprise/_index.md" >}}) is a commercial edition of Grafana that includes additional features not found in the open source version.
+
+Building on everything you already know and love about Grafana, Grafana Enterprise adds enterprise data sources, advanced authentication options, more permission controls, 24x7x365 support, and training from the core Grafana team.
+
+[Learn more about Grafana Enterprise](https://grafana.com/enterprise). To purchase Enterprise or obtain a trial license, contact the Grafana Labs [Sales Team](https://grafana.com/contact?about=support&topic=Grafana%20Enterprise).

docs/sources/shared/basics/what-is-grafana.md

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+---
+title: What is Grafana?
+---
+
+## What is Grafana?
+
+Grafana is open source visualization and analytics software. It allows you to query, visualize, alert on, and explore your metrics no matter where they are stored. In plain English, it provides you with tools to turn your time-series database (TSDB) data into beautiful graphs and visualizations.