Separate path.hh from content-address.hh

It is good to separate concerns; `StorePath` (in general) has nothing to
do with `ContentAddress` anyways.

This reduces the diff from #3746.

src/libstore/path.hh

@@ -1,6 +1,7 @@
 #pragma once
 
-#include "content-address.hh"
+#include <string_view>
+
 #include "types.hh"
 
 namespace nix {
@@ -66,8 +67,6 @@ public:
 typedef std::set<StorePath> StorePathSet;
 typedef std::vector<StorePath> StorePaths;
 
-typedef std::map<StorePath, std::optional<ContentAddress>> StorePathCAMap;
-
 /* Extension of derivations in the Nix store. */
 const std::string drvExtension = ".drv";
 

src/libstore/realisation.hh

@@ -1,5 +1,8 @@
 #pragma once
 
+#include <variant>
+
+#include "hash.hh"
 #include "path.hh"
 #include <nlohmann/json_fwd.hpp>
 #include "comparator.hh"

src/libstore/store-api.hh

@@ -87,6 +87,8 @@ enum BuildMode { bmNormal, bmRepair, bmCheck };
 struct BuildResult;
 
 
+typedef std::map<StorePath, std::optional<ContentAddress>> StorePathCAMap;
+
 struct StoreConfig : public Config
 {
     using Config::Config;