Vulkan: More trace points in the readpixels path Occassionally we hit a bad path in this case, this change makes it clearer from the traces which bad path is hit. Bug: b/310701311 Change-Id: Ic674d6396b0e88f1a1db3ded7efe195fb7397135 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5087207 Reviewed-by: Charlie Lao <cclao@google.com> Auto-Submit: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>