Vulkan: Fix ES 3.1 vertex attribute bindings When handling dirty bindings, we were treating binding indices as if they were attribute indices, causing strange behavior. This change fixes the dirty bit handler to use the provided index properly and update the attributes that correspond to the binding index. Test: ./angle_end2end_tests --gtest_filter='VertexAttributeTestES31.OnlyUpdate*/ES3_1_Vulkan' Bug: angleproject:3598 Change-Id: I2bc3cd4da5f639a1301776fcf057a74368812c56 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1718786 Commit-Queue: James Dong <dongja@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>