AzureMonitor: Added ARG query function for template variables (#53059) (#54204)

* Added ARG query functionfor template variables

* removed unused import

* Tweak tests

* Fix tests

* Renamed query function - added 'Azure'

* Revert "Renamed query function - added 'Azure'"

This reverts commit a046bcdd7c.

* Adressed comments

* Fix uncaught error issue

* revert last commit

* Add back errorMessage check

(cherry picked from commit d0d6562f63)

Co-authored-by: Yaelle Chaudy <42030685+yaelleC@users.noreply.github.com>

docs/sources/datasources/azuremonitor/template-variables.md

@@ -34,6 +34,7 @@ The Azure Monitor data source provides the following queries you can specify in
 | Metric Names    | Returns a list of metric names for a resource.                                               |
 | Workspaces      | Returns a list of workspaces for the specified subscription.                                 |
 | Logs            | Use a KQL query to return values.                                                            |
+| Resource Graph  | Use an ARG query to return values.                                                           |
 
 Any Log Analytics KQL query that returns a single list of values can also be used in the Query field. For example: