[FEA] Improve get_json_object_multiple_paths by customizing batch construction for strings columns

[ttnghia]

Currently, for constructing the output columns for get_json_object_multiple_paths, we call cudf::make_strings_column separately on separate output. Each of such calls involves several stream synchronization, thus the total process of creating the output is very inefficient.

We can do better by implementing a customized version for constructing a batch of strings columns at the same time, with minimal overhead of stream sync.