tests/gl_basic: reshuffle the cgl tests
tests/gl_basic: reshuffle the cgl tests

During context setup we prioritise as follows

 1. expected error (!= NO_ERROR), check it
 2. otherwise (if call fails) check for
 a) UNSUPPORTED_ON_PLATFORM and
 b) ERROR_UNKNOWN (winsys implementation has rejected the request)
 and skip the test. If other error is returned, fail the test.

Thus, we can fold the CGL specific UNSUPPORTED_ON_PLATFORM tests, where
NO_ERROR is expected. Thus all that happens is that some tests change
from "pass" to "skip", at the cost of greatly simplifying things ;-)

The remaining tests will still need to be separated as any other
expected result must be checked explicitly.

Add a similar inline comment for posterity.

Signed-off-by: Emil Velikov <f20878473f414da183da19ee25c8722cc1d711e4@collabora.com>
Reviewed-by: Chad Versace <a557f7f75bf28dc19ac99107f5cc7cd6b3fbdb1a@intel.com>

waffle-gl/waffle,waffle-gl/waffle,dcbaker/waffle,chadversary/waffle,dcbaker/waffle,dcbaker/waffle,chadversary/waffle,chadversary/waffle,waffle-gl/waffle,waffle-gl/waffle