Restrict some code to StoreDirConfig

- part of eval cache
 - part of derivations
 - derived path
 - store path with outputs
 - serializers

src/libexpr/value.hh

@@ -66,7 +66,6 @@ class Symbol;
 class PosIdx;
 struct Pos;
 class StorePath;
-class Store;
 class EvalState;
 class XMLWriter;