Option to fail on missing/failed AT application

[lynxplay]

Expose a configuration option in paperweight-core/patcher to fail if the application of access transformers via JST fails.
For this, --access-transformer-validation=error should be passed to JST for a representative exit code.

This should help during updates when a lot of AT targets become invalid as they were renamed/removed.

[Toffikk]

I opened a pr that aims to do just this #376, please lmk if i should modify anything or if you're satisfied with it