Add 8 unused bits to unsized GL_DEPTH_COMPONENT and sized
GL_DEPTH_COMPONENT24.

This results in the corresponding gl::InternalFormat exposing 4 bytes
per pixel and fixes a crash when serializing frame buffer depth
attachements in FrameCapture for GLES1 on Vulkan.

This patch fixes all comparisions crashing in the capture/replay GLES1
tests on SwiftShader.

Bug: angleproject:5799
Change-Id: I39c4309d5c7a1740dfd21c53f116b7e175b64847
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2794381Reviewed-by: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Lubosz Sarnecki <lubosz.sarnecki@collabora.com>