The motivation for this is that CompilationInfo really shouldn't
explicitly know anything about CodeStubs. This is evident in
the TurboFan stubs pipeline, which only needs to pass down
information about Code::Flags to the code generator and not
any of the CallInterfaceDescriptor silliness that Hydrogen has
to push around, since TF has the Linkage class that
encapsulates everything that is needed for the stub ABI. So,
instead of threading CodeStub machinery through the TF stub
pipeline, it is now removed from CompilationInfo and replaced
by only the explicit bits needed both by the Crankshaft and
TF pipelines in code generation.

Review URL: https://codereview.chromium.org/1604543002

Cr-Commit-Position: refs/heads/master@{#33410}