Stackdriver: Rename Stackdriver to Google Cloud Monitoring (#25807)

* Update backend

* Update frontend

* Keep old plugin id

* Update docs

* Place doc images to a new directory

* Legacy support for stackdriver-auto alignment

* Consistent plugin name

* Apply suggestions from code review

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>
Co-authored-by: Tobias Skarhed <1438972+tskarhed@users.noreply.github.com>

* Update docs

* Update public/app/plugins/datasource/cloud-monitoring/README.md

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>

* Add reference to the data source formerly being named Stackdriver

* Update pkg/models/datasource.go

Co-authored-by: Carl Bergquist <carl@grafana.com>

* Fix gofmt

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>
Co-authored-by: Tobias Skarhed <1438972+tskarhed@users.noreply.github.com>
Co-authored-by: Carl Bergquist <carl@grafana.com>

pkg/models/datasource.go

@@ -22,9 +22,11 @@ const (
 	DS_MSSQL         = "mssql"
 	DS_ACCESS_DIRECT = "direct"
 	DS_ACCESS_PROXY  = "proxy"
-	DS_STACKDRIVER   = "stackdriver"
-	DS_AZURE_MONITOR = "grafana-azure-monitor-datasource"
-	DS_LOKI          = "loki"
+	// Stackdriver was renamed Google Cloud monitoring 2020-05 but we keep
+	// "stackdriver" to avoid breaking changes in reporting.
+	DS_CLOUD_MONITORING = "stackdriver"
+	DS_AZURE_MONITOR    = "grafana-azure-monitor-datasource"
+	DS_LOKI             = "loki"
 )
 
 var (
@@ -97,7 +99,7 @@ var knownDatasourcePlugins = map[string]bool{
 	DS_POSTGRES:                              true,
 	DS_MYSQL:                                 true,
 	DS_MSSQL:                                 true,
-	DS_STACKDRIVER:                           true,
+	DS_CLOUD_MONITORING:                      true,
 	DS_AZURE_MONITOR:                         true,
 	DS_LOKI:                                  true,
 	"opennms":                                true,