oeqa/core: Add base OEQA framework

oeqa/core: Add base OEQA framework

case: Defines OETestCase base class that provides custom
    methods/attrs defined by the framework.
    Every OETestCase instance contains a reference to the test
    data (d), the test context (tc) and the logger.
    Also implements _oe{SetUp,TearDown}Class for make special
    handling of OEQA decorators and validations.

runner: Defines OETestRunner/OETestResult with support for RAW
    and XML result logs.

exception: Custom exceptions related to the OEQA framework based
    on class OEQAException.

[YOCTO #10230]
[YOCTO #10233]

(From OE-Core rev: c466086ccc4d4bb02d578a821cfb945945bfd529)

Signed-off-by: Aníbal Limón <anibal.limon@linux.intel.com>
Signed-off-by: Mariano Lopez <mariano.lopez@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>