The ANGLE_ENABLE_VULKAN_VALIDATION_LAYERS_BY_DEFAULT define shouldn't
be being checked in tests. Enable the debug layers by default.

Bug: angleproject:4227
Bug: angleproject:4229
Change-Id: I9717cb1c611ebd585a5c03ba2057036e1b086001
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1972497
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>