[Dependency Scanner] Refactor ModuleDependencies to represent binary-only Swift modules explicitly

This matches the behavior of the current client (`swift-driver`) and reduces ambiguity in how the nodes in the graph are to be treated. Swift dependencies with a textual interface, for example, must be built into a binary module by clients. Swift dependencies without a textual interface, with only a binary module, are to be used directly, without any up-to-date checks.

Note, this is distinct from Swift dependencies that have a textual interface, for which we also detect potential pre-build binary module candidates. Those are still reported in the `details` field of textual Swift dependencies as `prebuiltModuleCandidates`.

lib/Serialization/SerializedModuleLoader.cpp

@@ -394,8 +394,13 @@ llvm::ErrorOr<ModuleDependencies> SerializedModuleLoaderBase::scanModuleFile(
                        nullptr,
                        isFramework, loadedModuleFile);
 
+  const std::string moduleDocPath;
+  const std::string sourceInfoPath;
   // Map the set of dependencies over to the "module dependencies".
-  auto dependencies = ModuleDependencies::forSwiftModule(modulePath.str(), isFramework);
+  auto dependencies = ModuleDependencies::forSwiftBinaryModule(modulePath.str(),
+                                                               moduleDocPath,
+                                                               sourceInfoPath,
+                                                               isFramework);
   llvm::StringSet<> addedModuleNames;
   for (const auto &dependency : loadedModuleFile->getDependencies()) {
     // FIXME: Record header dependency?