This Cl adds utility classes to dump out SPIR-V disassembly of the
builder and instructions.
Bug: tint:5
Change-Id: Ib4c57025ac63cb0be456bd819461c98ffa94367f
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/17560
Reviewed-by: David Neto <dneto@google.com>