Restructure cloudmigration service (#83211)

* Restructure cloudmigation service

* Adjust codewoners and wire

* Comment out unused metrics

pkg/services/cloudmigration/cloudmigrationtest/fake.go

@@ -0,0 +1,15 @@
+package cloudmigrationtest
+
+import (
+	"context"
+
+	"github.com/grafana/grafana/pkg/services/cloudmigration"
+)
+
+type Service struct {
+	ExpectedError error
+}
+
+func (s *Service) MigrateDatasources(ctx context.Context, request *cloudmigration.MigrateDatasourcesRequest) (*cloudmigration.MigrateDatasourcesResponse, error) {
+	return nil, cloudmigration.ErrInternalNotImplementedError
+}