OrcStorage fails to detect schema in some cases

OrcStorage needs to detect the schema of input data paths. If some data paths have no ORC files (perhaps only a _SUCCESS marker is present), this will fail.

For example:

A = LOAD '/path/to/20230101,/path/to/20230102' USING OrcStorage();

If /path/to/20230101 contains only a _SUCCESS marker and 20230102 contains data, OrcStorage fails to detect the schema and Pig exits with a confusing/unhelpful error, something like "Cannot find any ORC files from <locations>. Probably multiple load/store statements in script."

The code tries to use a search algorithm to recursively search through all input paths for the data (via Utils.depthFirstSearchForFile), but it is implemented incorrectly and returns early in this scenario.

See: https://github.com/apache/pig/blob/c0d75ba930f9aa5c6454d0264a96f82b45279202/src/org/apache/pig/builtin/OrcStorage.java#L389-L408

https://github.com/apache/pig/blob/59ec4a326079c9f937a052194405415b1e3a2b06/src/org/apache/pig/impl/util/Utils.java#L629-L667

I'll attach a patch.