drm/xe/tests: Test both CPU- and GPU page-table updates with the migrate test

Add a test parameter to force GPU page-table updates with the migrate
test and test both CPU- and GPU updates. Also provide some timing
results.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>