Azure: Load custom clouds from ini file (#87667)

* Load custom clouds from config file

* Update docs

* Use the correct list of clouds, add test, fix error condition handling

* Remove on custom cloud from sample.ini and docs

* Remove unnecessary else block

* Use cached json instead of serializing with each request

* Update grafana-azure-sdk-go version to v2.0.4

* update configure-grafana entry for clouds_config

* fix lint errors

* fix lint errors

---------

Co-authored-by: Jeremy Angel (from Dev Box) <jeremyangel@microsoft.com>

conf/sample.ini

@@ -839,6 +839,22 @@
 # Default value is AzureCloud (i.e. public cloud)
 ;cloud = AzureCloud
 
+# A customized list of Azure cloud settings and properties, used by data sources which need this information when run in non-standard azure environments
+# When specified, this list will replace the default cloud list of AzureCloud, AzureChinaCloud, AzureUSGovernment and AzureGermanCloud
+;clouds_config = `[
+;		{
+;			"name":"CustomCloud1",
+;			"displayName":"Custom Cloud 1",
+;			"aadAuthority":"https://login.cloud1.contoso.com/",
+;			"properties":{
+;				"azureDataExplorerSuffix": ".kusto.windows.cloud1.contoso.com",
+;				"logAnalytics":            "https://api.loganalytics.cloud1.contoso.com",
+;				"portal":                  "https://portal.azure.cloud1.contoso.com",
+;				"prometheusResourceId":    "https://prometheus.monitor.azure.cloud1.contoso.com",
+;				"resourceManager":         "https://management.azure.cloud1.contoso.com"
+;			}
+;		}]`
+
 # Specifies whether Grafana hosted in Azure service with Managed Identity configured (e.g. Azure Virtual Machines instance)
 # If enabled, the managed identity can be used for authentication of Grafana in Azure services
 # Disabled by default, needs to be explicitly enabled