Move access-path filtering into ModuleNameLookup (out of lookupValue) (#27097)

Removes duplicated logic from the implementations of
FileUnit::lookupValue, and simplifies the interface to
ModuleDecl::lookupValue, where everyone was passing an empty
(non-filtering) access path anyway /except/ during actual lookup from
source code. No functionality change.

lib/Serialization/SerializedModuleLoader.cpp

@@ -946,12 +946,8 @@ bool SerializedASTFile::isSystemModule() const {
   return false;
 }
 
-void SerializedASTFile::lookupValue(ModuleDecl::AccessPathTy accessPath,
-                                    DeclName name, NLKind lookupKind,
+void SerializedASTFile::lookupValue(DeclName name, NLKind lookupKind,
                                     SmallVectorImpl<ValueDecl*> &results) const{
-  if (!ModuleDecl::matchesAccessPath(accessPath, name))
-    return;
-  
   File.lookupValue(name, results);
 }