twister: qemu: add QEMU support on Windows in twister

Twister does not support running tests on QEMU on Windows.
Add a new twister handler called QEMUWinHandler which supports running
tests on Windows. Enable running tests in testinstance, only if
QEMU_BIN_PATH environment variable exists on Windows.
Modify pytest test for testinstance to reflect the change in
runnability of QEMU on Windows.
Tested by running several Ztest and console harness tests.

Signed-off-by: Michal Smola <michal.smola@nxp.com>