Update SPIRV caching to use SkWriter32/SkReader32 and allow inspection

Change-Id: I6656d971c05f0ed3515f095ffcd41ae73a5c483f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/206687
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
3 files changed