[clang][deps] Split lookupModuleOutput out of DependencyConsumer NFC

The idea is to split the callbacks that are used to consume dependency
information (DependencyConsumer) from callbacks that modify the scan
behaviour itself in any way (DependencyActionController). Currently this
is just lookupModuleOutput, but we have additional callbacks related to
CAS support that we intend to upstream in the future.

Differential Revision: https://reviews.llvm.org/D144058