Improve test coverage of binary data parsers

[joachimmetz]

Now with dtFabric support, we can generate data format structs for testing e.g. https://github.com/libyal/dtformats/blob/master/tests/rp_log.py#L25

Per https://github.com/log2timeline/plaso/issues/2207, let's improve test coverage

• [ ] ASL
  • https://github.com/log2timeline/plaso/pull/2227
• [x] CUPS IPP
  • https://github.com/log2timeline/plaso/pull/2225
• [ ] TODO

[joachimmetz]

This can be applied to non-dtFabric-based binary data parsers as well.

TODO:

• @joachimmetz to implement the first couple of test improvement and extend dtFabric where needed
• @aguilajesus if you want to help out, let me know