tests/drv_hangman: Convert test from shell script to c

Mixing script and standlone tests didn't mix well with the
strict i915_ring_stop flags handling. Also squash drv_missed_irq_hang
to the new test.

v2: - Remove missed irq test (Daniel Vetter)
    - gitignore fixed (Oscar Mateo)
    - fix check_other_clients to handle dangling fd's

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=78322
Suggested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Oscar Mateo <oscar.mateo@intel.com> <v1>
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>

tests/Makefile.sources

@@ -17,6 +17,7 @@ NOUVEAU_TESTS_M = \
 TESTS_progs_M = \
 	core_get_client_auth \
 	drv_suspend \
+	drv_hangman \
 	gem_bad_reloc \
 	gem_basic \
 	gem_caching \
@@ -149,7 +150,6 @@ TESTS_scripts_M = \
 TESTS_scripts = \
 	debugfs_emon_crash \
 	drv_debugfs_reader \
-	drv_hangman \
 	drv_missed_irq_hang \
 	drv_module_reload \
 	kms_sysfs_edid_timing \