Validate CKAN-meta PRs with netkan.exe

[HebaruSan]

With KSP-CKAN/CKAN#2819 merged, we can now use netkan.exe --validate-ckan to validate .ckan files according to the tests in KSP-CKAN/CKAN#2788.

This pull request does that for pull requests in the CKAN-meta repo. Since netkan.exe performs schema validation, CKAN.schema and ckan-validate.py are no longer downloaded or used.

There was some discussion of erroring out if the .ckan file doesn't exactly match the nicely sorted pretty-printed output of netkan.exe. For now this is not done; we have a lot of old metadata, and it would be annoying for maintenance if we could not make simple small changes to such files and merge them.

[techman83]

There was some discussion of erroring out if the .ckan file doesn't exactly match the nicely sorted pretty-printed output of netkan.exe. For now this is not done; we have a lot of old metadata, and it would be annoying for maintenance if we could not make simple small changes to such files and merge them.

I'm less concerned by this. All of our old metadata was reprocessed when I built a bot to back fill all the hashes and upload to archive.org where license allowed. Anything that doesn't have a hash is likely dead metadata and likely not something we'll be altering anytime soon. So the otherwhelming majority of the metadata has been produced by NetKAN in some shape or form (be that via the indexer, the backfill bot or via PR).

This pull request does that for pull requests in the CKAN-meta repo. Since netkan.exe performs schema validation, CKAN.schema and ckan-validate.py are no longer downloaded or used.

Woooooooo!