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>

docs/sources/setup-grafana/configure-grafana/_index.md

@@ -1175,6 +1175,28 @@ Azure cloud environment where Grafana is hosted:
 | US Government cloud                              | AzureUSGovernment      |
 | Microsoft German national cloud ("Black Forest") | AzureGermanCloud       |
 
+### clouds_config
+
+The JSON config defines a list of Azure clouds and their associated properties when hosted in custom Azure environments.
+
+For example:
+
+```ini
+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"
+			}
+		}]`
+```
+
 ### managed_identity_enabled
 
 Specifies whether Grafana hosted in Azure service with Managed Identity configured (e.g. Azure Virtual Machines instance). Disabled by default, needs to be explicitly enabled.