SpirvShader doesn't actually do anything with this (yet).
Extracts the dull plumbing from the meat of the SpirvShader debugger implementation.

Bug: b/145351270
Change-Id: I1a648d8e463c428a232f711d0cc5dd0ecf94ad1e
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/38914Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Ben Clayton <bclayton@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>