WebGPU: Stream incompatible vertex and index data. Support reading back index and vertex buffers to stream incompatible source data. For now this includes: * Non-multiple-of-4 stride vertex data * Stride not a multiple of the type size * Unsigned byte indices Fix fallback formats so that all GLES formats have a fallback. Fix CopyToFloatVertexData writing the alpha channel as Float32One with a static_cast which converted Float32One (an integer) to a float instead of bit-casting. Bug: angleproject:368602384 Change-Id: I7eb1ba7ad1ec4292060c18de22f5948136cbb0a3 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6194556 Reviewed-by: Liza Burakova <liza@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>