tests/pm_pc8: add some more stress tests
tests/pm_pc8: add some more stress tests

I was suspecting some problems just happen if we have a bigger wait
than the current ones we have, so add a new WAIT_EXTRA flag just to
see if the problems really happen. Also, add support for the wait
flags on the gem stress tests, and use them.

Signed-off-by: Paulo Zanoni <cc0e04a2103c45cd195651d976f79813d0f66bdf@intel.com>

yipdw/intel-gpu-tools,chenxianqin/intel-gpu-tools,rib/intel-gpu-tools,mv0/intel-gpu-tools,chenxianqin/intel-gpu-tools,erikarn/intel-gpu-tools,mv0/intel-gpu-tools,tiagovignatti/intel-gpu-tools,rib/intel-gpu-tools,mv0/intel-gpu-tools,rib/intel-gpu-tools,yipdw/intel-gpu-tools,dlespiau/checkmate-test-igt,chenxianqin/intel-gpu-tools,yipdw/intel-gpu-tools,dlespiau/checkmate-test-igt,dlespiau/checkmate-test-igt,tiagovignatti/intel-gpu-tools,erikarn/intel-gpu-tools,tiagovignatti/intel-gpu-tools,erikarn/intel-gpu-tools,erikarn/intel-gpu-tools,dlespiau/checkmate-test-igt,chenxianqin/intel-gpu-tools,tiagovignatti/intel-gpu-tools,mv0/intel-gpu-tools,yipdw/intel-gpu-tools,rib/intel-gpu-tools