Vulkan: Fix chunkIndex is not 16 bits when computing key Replace `uint8_t` with `size_t` in `ComputePipelineCacheVkChunkKey()`. This fixes the bug and also makes type consistent with the rest of the code. Also `CacheDataHeader::setData()` made consistent with `getData()`. Bug: b/246683126 Change-Id: Ib1f8b680622c3d4f912d8a21ed8b740c3d17483e Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5854707 Reviewed-by: Amirali Abdolrashidi <abdolrashidi@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>