CloudMigration: Provide a stats rollup in the GetSnapshot response (#90252)

* order session list descending

* add snapshot status method to store

* query stats while retrieving snapshot

* return stats in dto

* swagger

* fix tests

* commit results of bingo get

* fix swagger

* minor improvement

* fix typo

* forgot a file

pkg/services/cloudmigration/api/dtos.go

@@ -299,7 +299,13 @@ type GetSnapshotResponse struct {
 
 type GetSnapshotResponseDTO struct {
 	SnapshotDTO
-	Results []MigrateDataResponseItemDTO `json:"results"`
+	Results     []MigrateDataResponseItemDTO `json:"results"`
+	StatsRollup SnapshotResourceStats        `json:"stats"`
+}
+
+type SnapshotResourceStats struct {
+	Types    map[MigrateDataType]int `json:"types"`
+	Statuses map[ItemStatus]int      `json:"statuses"`
 }
 
 // swagger:parameters getShapshotList