Implement bulk delete (#7607)

Bulk delete at storage level in Multiple Delete Objects API

In order to accelerate bulk delete in Multiple Delete objects API,
a new bulk delete is introduced in storage layer, which will accept
a list of objects to delete rather than only one. Consequently,
a new API is also need to be added to Object API.

cmd/utils.go

@@ -474,3 +474,10 @@ func restQueries(keys ...string) []string {
 	}
 	return accumulator
 }
+
+// Reverse the input order of a slice of string
+func reverseStringSlice(input []string) {
+	for left, right := 0, len(input)-1; left < right; left, right = left+1, right-1 {
+		input[left], input[right] = input[right], input[left]
+	}
+}