oeqa/core: Implement proper extra result collection and serialization
Implement handling of extra result (e.g. ptestresult) collection with
the addition of a "extraresults" extraction function in OETestResult. In
order to be able to serialize and deserialize the extraresults data,
allow OETestResult add* calls to take a details kwarg. The subunit
module can handle cross-process transfer of binary data for the details
kwarg. With a TestResult proxy class to sit inbetween to encode and
decode to and from json.
Signed-off-by: Nathan Rossi <nathan@nathanrossi.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
