Change gl_tests and gl_unittests isolate type to windowed_test_launcher

Since these tests use the native windowing system and thus need Xvfb
when they run on GCEs.

And also because these tests need to be wrapped by test_env.py to set up
correct environment variables on ASAN, TSAN and CFI bots.
gl_unittests already had it, but gl_tests did not, since they were "raw"
isolate type.

Unfortunately, gl_unittests had to be removed from 'Linux MSan Tests' as
the result, for the same reason gl_tests were removed in
crbug.com/830659. Probably a meaningful codepath was not tested before
anyway.

On another hand, gl_unittests can pass on GCEs now, so also removed the
exception to launch them on HW GPU machines for Linux CFI bots, making
them consistent with ASAN and TSAN bots.

Also had to suppress a leak in NVIDIA libraries, since ASAN now really
runs and detects it.

And a minor cleanup removing 'use_xvfb' flag which is irrelevant for
Swarming bots.

Bug: 1081054
Change-Id: Iec8c2e3f54505eca6ae22333c86759a9553ed799
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2199670
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#772973}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 37e04345548f8f6893dcde125056d1813fc6f663

sanitizers/lsan_suppressions.cc

@@ -30,6 +30,8 @@ char kLSanDefaultSuppressions[] =
 
     // Leaks in Nvidia's libGL.
     "leak:libGL.so\n"
+    "leak:libGLX_nvidia.so\n"
+    "leak:libnvidia-glcore.so\n"
 
     // XRandR has several one time leaks.
     "leak:libxrandr\n"