Docs: Rewrite alerting docs (#24653)

* updated menu and added alerts-overview.md

* Delete metrics.md

* Update menu.yaml

* changed file name and updated menu

* Update create-alerts.md

* added file and link

* Create view-alerts.md

* added content and links

* Update pause-an-alert.md

* added content and links

* edited notification content

* updated link

* Update docs/sources/alerting/create-alerts.md

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>

* Applied marcus e. edits

* Update docs/sources/alerting/alerts-overview.md

Co-authored-by: Carl Bergquist <carl@grafana.com>

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>
Co-authored-by: Carl Bergquist <carl@grafana.com>

docs/sources/installation/requirements.md

@@ -39,7 +39,7 @@ Minimum recommended CPU: 1
 Some features might require more memory or CPUs. Features require more resources include:
 
 - [Server side rendering of images]({{< relref "../administration/image_rendering/#requirements" >}})
-- [Alerting]({{< relref "../alerting/rules" >}})
+- [Alerting]({{< relref "../alerting/alerts-overview" >}})
 - Data source proxy
 
 ## Supported databases