refactor(3p/nix): Anchor local includes at src/

Previously all includes were anchored in one global mess of header
files. This moves the includes into filesystem "namespaces" (if you
will) for each sub-package of Nix.

Note: This commit does not introduce the relevant build system changes.

third_party/nix/src/nix-store/dotgraph.cc

@@ -1,9 +1,9 @@
-#include "dotgraph.hh"
+#include "nix-store/dotgraph.hh"
 
 #include <iostream>
 
-#include "store-api.hh"
-#include "util.hh"
+#include "libstore/store-api.hh"
+#include "libutil/util.hh"
 
 using std::cout;
 

third_party/nix/src/nix-store/dotgraph.hh

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "types.hh"
+#include "libutil/types.hh"
 
 namespace nix {
 

third_party/nix/src/nix-store/graphml.cc

@@ -1,10 +1,10 @@
-#include "graphml.hh"
+#include "nix-store/graphml.hh"
 
 #include <iostream>
 
-#include "derivations.hh"
-#include "store-api.hh"
-#include "util.hh"
+#include "libstore/derivations.hh"
+#include "libstore/store-api.hh"
+#include "libutil/util.hh"
 
 using std::cout;
 

third_party/nix/src/nix-store/graphml.hh

@@ -1,6 +1,6 @@
 #pragma once
 
-#include "types.hh"
+#include "libutil/types.hh"
 
 namespace nix {
 

third_party/nix/src/nix-store/nix-store.cc

@@ -7,18 +7,18 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 
-#include "archive.hh"
-#include "derivations.hh"
-#include "dotgraph.hh"
-#include "globals.hh"
-#include "graphml.hh"
-#include "legacy.hh"
-#include "local-store.hh"
-#include "monitor-fd.hh"
-#include "serve-protocol.hh"
-#include "shared.hh"
-#include "util.hh"
-#include "worker-protocol.hh"
+#include "libmain/shared.hh"
+#include "libstore/derivations.hh"
+#include "libstore/globals.hh"
+#include "libstore/local-store.hh"
+#include "libstore/serve-protocol.hh"
+#include "libstore/worker-protocol.hh"
+#include "libutil/archive.hh"
+#include "libutil/monitor-fd.hh"
+#include "libutil/util.hh"
+#include "nix-store/dotgraph.hh"
+#include "nix-store/graphml.hh"
+#include "nix/legacy.hh"
 
 #if HAVE_SODIUM
 #include <sodium.h>