Cloud Migrations: Create new service for cloud migrations (#80949)

* introduce feature toggle

* create base service structure

* fix sample metric

* register metrics

* add to codeowners

* separate api dtos from service models

* remove leading newline

pkg/services/cloudmigrations/api/api_test.go

@@ -0,0 +1,12 @@
+package api
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_OnlyEnabledForGrafanaAdmi(t *testing.T) {
+	// TODO: implement
+	assert.True(t, true)
+}