Docs: Combines thresholds docs into a single topic (#47985)

* start updates

* combines content into single topic

* completes draft update

* Update docs/sources/panels/configure-thresholds/_index.md

Co-authored-by: Torkel Ödegaard <torkel@grafana.com>

* incorporates feedback

* Update docs/sources/panels/configure-thresholds/_index.md

Co-authored-by: Torkel Ödegaard <torkel@grafana.com>

* Update docs/sources/panels/configure-thresholds/_index.md

Co-authored-by: Torkel Ödegaard <torkel@grafana.com>

* Update docs/sources/panels/configure-thresholds/_index.md

Co-authored-by: Torkel Ödegaard <torkel@grafana.com>

* incorporates final feedback

Co-authored-by: Torkel Ödegaard <torkel@grafana.com>

docs/sources/best-practices/dashboard-management-maturity-levels.md

@@ -46,7 +46,7 @@ How can you tell you are here?
 
 - Compare like to like: split service dashboards when the magnitude differs. Make sure aggregated metrics don't drown out important information.
 - Expressive charts with meaningful use of color and normalizing axes where you can.
-  - Example of meaningful color: Blue means it's good, red means it's bad. [Thresholds]({{< relref "../panels/specify-thresholds/about-thresholds.md" >}}) can help with that.
+  - Example of meaningful color: Blue means it's good, red means it's bad. [Thresholds]({{< relref "../panels/configure-thresholds" >}}) can help with that.
   - Example of normalizing axes: When comparing CPU usage, measure by percentage rather than raw number, because machines can have a different number of cores. Normalizing CPU usage by the number of cores reduces cognitive load because the viewer can trust that at 100% all cores are being used, without having to know the number of CPUs.
 - Directed browsing cuts down on "guessing."
   - Template variables make it harder to “just browse” randomly or aimlessly.