drm/ttm/tests: Add tests with mock resource managers

drm/ttm/tests: Add tests with mock resource managers

Add mock resource manager to test ttm_bo_validate() with non-system
placements. Update KConfig entry to enable DRM Buddy allocator, used
by the mock manager. Update move function to do more than just assign
a resource.

Signed-off-by: Karolina Stolarek <karolina.stolarek@intel.com>
Tested-by: Somalapuram, Amaranath <asomalap@amd.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/664791dbb7cbada29e705d2fcaf176023f1b8649.1718192625.git.karolina.stolarek@intel.com