use testedClDevice instead of devices[testedRootDeviceIndex]
pass only tested device to build program
add member ApiFixture::pDevice
Related-To: NEO-4632
Change-Id: I7d8d1bd6c3336970a1ad0f0e48c254eb6f419200
Signed-off-by: Mateusz Jablonski <mateusz.jablonski@intel.com>