This is a callable that manages file caching operations.
Declared in <llvm/Support/Caching.h>
using FileCacheFunction = std::function<Expected<AddStreamFn>(unsigned int, StringRef, Twine const&)>;It accepts a task ID Task, a unique key Key, and a module name ModuleName, and returns AddStreamFn(). This function determines whether a cache hit or miss occurs and handles the appropriate actions.