Vulkan: Switch XFB counter buffer to suballocation Bug: b/205337962 Change-Id: I2e26fa3ab150b858f07665459fa108440af988d5 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3402333 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Ian Elliott <ianelliott@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Charlie Lao <cclao@google.com>