Shared Azure middleware between Azure Monitor and Prometheus datasources (#46002)

* Scopes in Azure middleware

* Enable Azure middleware without feature flag

* Use common Azure middleware in Azure Monitor

* Apply feature flag to JsonData configuration of Azure auth

* Enforce feature flag in Prometheus datasource

* Prometheus provider tests

* Datasource service tests

* Fix http client provider tests

* Pass sdkhttpclient.Options by reference

* Add middleware to httpclient.Options

* Remove dependency on Grafana settings

* Unit-tests updated

* Fix ds_proxy_test

* Fix service_test

pkg/setting/setting_azure_test.go

@@ -3,6 +3,7 @@ package setting
 import (
 	"testing"
 
+	"github.com/grafana/grafana/pkg/tsdb/azuremonitor/azsettings"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -17,27 +18,27 @@ func TestAzureSettings(t *testing.T) {
 			{
 				name:            "should be Public if not set",
 				configuredValue: "",
-				resolvedValue:   AzurePublic,
+				resolvedValue:   azsettings.AzurePublic,
 			},
 			{
 				name:            "should be Public if set to Public",
-				configuredValue: AzurePublic,
-				resolvedValue:   AzurePublic,
+				configuredValue: azsettings.AzurePublic,
+				resolvedValue:   azsettings.AzurePublic,
 			},
 			{
 				name:            "should be Public if set to Public using alternative name",
 				configuredValue: "AzurePublicCloud",
-				resolvedValue:   AzurePublic,
+				resolvedValue:   azsettings.AzurePublic,
 			},
 			{
 				name:            "should be China if set to China",
-				configuredValue: AzureChina,
-				resolvedValue:   AzureChina,
+				configuredValue: azsettings.AzureChina,
+				resolvedValue:   azsettings.AzureChina,
 			},
 			{
 				name:            "should be US Government if set to US Government using alternative name",
 				configuredValue: "usgov",
-				resolvedValue:   AzureUSGovernment,
+				resolvedValue:   azsettings.AzureUSGovernment,
 			},
 			{
 				name:            "should be same as set if not known",