Refactor hid.py (#1068)

* Small memory and performance improvements, mostly const() and bytearray
  ops.
* Separate out report specific code into report classes. Serves as a base
  for easier addition of custom endpoints in "the future".
* Lots of small integration changes, for example a simpler mechanism to
  record reports for unit tests (now with potential to verify other
  reports than 6KRO).