Enable drawRangeElements() for the Vulkan backend and the associated
tests.

Test: angle_deqp_gles3_tests
Bug: angleproject:3420
Change-Id: I98770631ce1387131bb45e2c1e9df24e911bc692
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1595101
Commit-Queue: Tim Van Patten <timvp@google.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>