heal: Move CheckParts from single handler to streaming RPC (#20755)

CheckParts call can take time to verify 10k parts of a single object in a single drive.
To avoid an internal dealine of one minute in the single handler RPC, this commit will
switch to streaming RPC instead.

internal/grid/handlers.go

@@ -115,6 +115,7 @@ const (
 	HandlerCheckParts2
 	HandlerRenamePart
 	HandlerClearUploadID
+	HandlerCheckParts3
 
 	// Add more above here ^^^
 	// If all handlers are used, the type of Handler can be changed.
@@ -196,6 +197,7 @@ var handlerPrefixes = [handlerLast]string{
 	HandlerRenameDataInline:            storagePrefix,
 	HandlerRenameData2:                 storagePrefix,
 	HandlerCheckParts2:                 storagePrefix,
+	HandlerCheckParts3:                 storagePrefix,
 	HandlerRenamePart:                  storagePrefix,
 	HandlerClearUploadID:               peerPrefix,
 }