Shuffle ValidPathInfo JSON rendering

`Store::pathInfoToJSON` was a rather baroque functions, being full of
parameters to support both parsed derivations and `nix path-info`. The
common core of each, a simple `dValidPathInfo::toJSON` function, is
factored out, but the rest of the logic is just duplicated and then
specialized to its use-case (at which point it is no longer that
duplicated).

This keeps the human oriented CLI logic (which is currently unstable)
and the core domain logic (export reference graphs with structured
attrs, which is stable), separate, which I think is better.

src/libstore/store-api.hh

@@ -80,7 +80,6 @@ typedef std::map<std::string, StorePath> OutputPathMap;
 
 enum CheckSigsFlag : bool { NoCheckSigs = false, CheckSigs = true };
 enum SubstituteFlag : bool { NoSubstitute = false, Substitute = true };
-enum AllowInvalidFlag : bool { DisallowInvalid = false, AllowInvalid = true };
 
 /**
  * Magic header of exportPath() output (obsolete).
@@ -665,28 +664,6 @@ public:
     std::string makeValidityRegistration(const StorePathSet & paths,
         bool showDerivers, bool showHash);
 
-    /**
-     * Write a JSON representation of store path metadata, such as the
-     * hash and the references.
-     *
-     * @param includeImpureInfo If true, variable elements such as the
-     * registration time are included.
-     *
-     * @param showClosureSize If true, the closure size of each path is
-     * included.
-     */
-    nlohmann::json pathInfoToJSON(const StorePathSet & storePaths,
-        bool includeImpureInfo, bool showClosureSize,
-        HashFormat hashFormat = HashFormat::Base32,
-        AllowInvalidFlag allowInvalid = DisallowInvalid);
-
-    /**
-     * @return the size of the closure of the specified path, that is,
-     * the sum of the size of the NAR serialisation of each path in the
-     * closure.
-     */
-    std::pair<uint64_t, uint64_t> getClosureSize(const StorePath & storePath);
-
     /**
      * Optimise the disk space usage of the Nix store by hard-linking files
      * with the same contents.