Experiment with removing preresolved dependency optimization

[tetsuo-cpp]

Currently we avoid invoking dependency resolution with hashed dependencies or when --no-deps are provided. This causes some inconsistency since pip is more accurate at finding dependencies than our hand-coded logic. Now that we've removed our own dependency resolution logic and are just shelling out to pip, we should experiment with removing this special case to see what the performance impact is like for large requirements files. If the slowdown is acceptable, we should consider removing the special case and repurposing the hashing logic and --no-deps flag to just pass this same flag down to the pip invocation.