CloudMigrations: Store encryption key in unified secrets table (#90908)

* store encryption key in unified secrets table

* fix local dev mode

* make metadata more realistic

* fix tests

* fix sql queries against postgres

* fix stats endpoint

pkg/services/cloudmigration/model.go

@@ -37,7 +37,7 @@ type CloudMigrationSnapshot struct {
 	UID            string `xorm:"uid"`
 	SessionUID     string `xorm:"session_uid"`
 	Status         SnapshotStatus
-	EncryptionKey  []byte `xorm:"encryption_key"` // stored in the unified secrets table
+	EncryptionKey  []byte `xorm:"-"` // stored in the unified secrets table
 	LocalDir       string `xorm:"local_directory"`
 	GMSSnapshotUID string `xorm:"gms_snapshot_uid"`
 	ErrorString    string `xorm:"error_string"`