Generate a synthetic file containing the spirv disassembly, and allow the debugger to single line step over these instructions, along with inspection of the SSA values.

All of this is no-op unless ENABLE_VK_DEBUGGER is defined at compile time, and the VK_DEBUG_PORT env var is set at run time.

Bug: b/145351270
Change-Id: Iba71717d78f7213ba586a1632b44f5fe08addf08
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/38915
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Ben Clayton <bclayton@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>