tests: skip test_json in both nitg-s and nitg-e
tests: do not skip opengles2_hello_triangle in nitg-s

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
nitg: activate FFI in all engines

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
nitg: collect_super_send detects callbacks to super from C

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>