Develop Chandra error parsing for BaseProduct parse_stderr

[DavidT3]

In theory, XGA product classes can take the stdout and stderr from the process that created them, check through it, and parse out errors that are actually a problem. Then for XGA generation those errors get raised and the process stops.

This works very well for SAS processes, because they use the stderr properly, and also provide a list of most errors that can be thrown.

eROSITA don't do that and it was a pain.

Will need to figure out what to do for Chandra!