oeqa/utils/testexport.py: add functionality for exporting binaries

oeqa/utils/testexport.py: add functionality for exporting binaries

This new file is encapsulating functionality for both
running tests with binaries support via TestNeedsBin() decorator
and exporting these binaries via testimage.bbclass file.
Addresses [YOCTO #7850], [YOCTO #8478], [YOCTO #8481],
[YOCTO #8536], [YOCTO #8694].

(From OE-Core rev: 14640f16b5ce09a14f88b3fa641d4cf2780f8b97)

Signed-off-by: Costin Constantin <costin.c.constantin@intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>