kms_atomic: Add basic atomic modesetting tests

Add tests for KMS atomic modesetting, to exercise the basic interface
and test failure/corner cases. Should ensure coherency between the
legacy and atomic interfaces.

v2: New patch.
v3: Disable connector checking for now, as it was causing GPU hangs on
    newer kernels.
v4: Rebase.
v5: Use do_ioctl or do_ioctl_err consistently. Use igt_assert_*()
    helper macros rather than igt_assert() directly.
    Move assertions into helper/check functions. Define atomic commit
    helper.
v6: Use do_ioctl_err, and define macros to move errors to
    actual callsite, rather than helper functions.

Co-authored-by: Micah Fedke <micah.fedke@collabora.com>
Signed-off-by: Daniel Stone <daniels@collabora.com>

tests/.gitignore

@@ -126,6 +126,7 @@ gen3_render_tiledy_blits
 gen7_forcewake_mt
 kms_3d
 kms_addfb_basic
+kms_atomic
 kms_crtc_background_color
 kms_cursor_crc
 kms_draw_crc

tests/Makefile.sources

@@ -63,6 +63,7 @@ TESTS_progs_M = \
 	gem_userptr_blits \
 	gem_write_read_ring_switch \
 	kms_addfb_basic \
+	kms_atomic \
 	kms_cursor_crc \
 	kms_draw_crc \
 	kms_fbc_crc \