This both speeds up test execution and cuts down on the number of new
windows and displays created for a test config. This feature is only
currently enabled for Windows NVIDIA and Intel. On every other config
there were blocking issues that would need investigation. Several tests
were manually flagged as needed new displays on each iteration to
prevent test flakiness.

This feature might fix the issues with Intel test flakiness that have
been prominent on the ANGLE CQ.

WGL configurations have also been removed from ANGLE tests. So this
removes more of the code from ANGLETest.cpp.

Bug: angleproject:3261
Change-Id: Ic2864d4806ad38e0eeaa3c0afcd54ae1c548090f
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1520995
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>