oeqa/core: Add loader, context and decorator modules

oeqa/core: Add loader, context and decorator modules

loader: Implements OETestLoader handling OETestDecorator
and filtering support when load tests. The OETestLoader is
responsible to set custom methods, attrs of the OEQA
frameowork.

[YOCTO #10231]
[YOCTO #10317]
[YOCTO #10353]

decorator: Add base class OETestDecorator to provide a common
way to define decorators to be used over OETestCase's, every
decorator has a method to be called when loading tests and
before test execution starts. Special decorators could be
implemented for filter tests on loading phase.

context: Provides HIGH level API for loadTests and runTests
of certain test component (i.e. runtime, sdk, selftest).

[YOCTO #10230]

(From OE-Core rev: 275ef03b77ef5f23b75cb01c55206d1ab0261342)

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>