Capture error details from SharpZipLib for invalid ZIPs

[HebaruSan]

Problem

We continue to have occasional difficulties with ZIP file validation. #2285 highlights an issue of discrepant redundant data in the local file header versus the central directory.

These issues are difficult to diagnose. In 1.22.6, the exceptions look like:

CKAN.FileNotFoundKraken: Trying to install CivilianPopulation 2.0.12, but it's not downloaded or download is corrupted

And in HEAD, we have:

Unhandled Exception: CKAN.InvalidModuleFileKraken: C:\Users\User\AppData\Local\Temp\tmpF3A6.tmp is not a valid ZIP file: ZipFile.TestArchive(true) returned false

These are pretty generic errors, which don't tell us much other than something is wrong with the ZIP. Lots of leg work is left to do to figure out what's wrong.

Changes

Now we capture more details from SharpZipLib, allowing us to specify which entry in the ZIP had a problem, as well as which validation step was being done and the detailed message from the validation function:

CKAN.InvalidModuleFileKraken: /tmp/tmp14ac6bce.tmp is not a valid ZIP file: Error in step EntryHeader for CivilianPopulation/Experience/Traits.cfg: Exception during test - 'Extract version mismatch'

At a code level this is fairly awkward as error reporting goes. ZipFile.TestArchive doesn't throw exceptions and it returns only a bool. To capture its error messages, we need to pass a delegate as its third parameter, which receives incremental status updates as it goes through each file. When it finds an error, the delegate is called with the error message, and we save it off and use it for our return parameter.

Not a fix for #2285, but it's probably the closest we'll get.