Fix up all calls to `assert()` in [LLVM,Subzero]Reactor.cpp with an appropriate call to one of these macros.

Bug: b/127433389
Change-Id: I188add3929c46932b8de5acf2ac4b2ac83b0768b
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/29055
Presubmit-Ready: Ben Clayton <bclayton@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Tested-by: Ben Clayton <bclayton@google.com>