Trace Tests: Add option for ASAN builds. ASAN builds can detect OOB memory accesses. This is very useful for diagnosing some kinds of flaky OOB crashes. Removes a test that was calling BufferSubData with a null data argument. This behaviour is undefined and we shouldn't be testing it. Also includes some minor refactorings and script changes. Bug: angleproject:5133 Change-Id: I5a7d9a5500c50a51f6369e944a5f0a533709f00d Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3002510 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Gert Wollny <gert.wollny@collabora.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>