Provides a number of standard debug macros.

assert_has_bound_scheduler() is stubbed as it depends on the Scheduler (coming in a later change).

Bug: b/139010488
Change-Id: I1854404477efb982c26e7ad3273c2ca544fd1725
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/34770Tested-by: Ben Clayton <bclayton@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>