refactor: Replace <filesystem> with <util/fs.h>

All code in this repo uses <util/fs.h>, except for a few lines. This is
confusing and potentially dangerous, if the safe <util/fs.h> wrappers
are not used.

src/bitcoin-chainstate.cpp

@@ -26,13 +26,13 @@
 #include <scheduler.h>
 #include <script/sigcache.h>
 #include <util/chaintype.h>
+#include <util/fs.h>
 #include <util/thread.h>
 #include <validation.h>
 #include <validationinterface.h>
 
 #include <cassert>
 #include <cstdint>
-#include <filesystem>
 #include <functional>
 #include <iosfwd>
 #include <memory>
@@ -50,8 +50,8 @@ int main(int argc, char* argv[])
             << "           BREAK IN FUTURE VERSIONS. DO NOT USE ON YOUR ACTUAL DATADIR." << std::endl;
         return 1;
     }
-    std::filesystem::path abs_datadir = std::filesystem::absolute(argv[1]);
-    std::filesystem::create_directories(abs_datadir);
+    fs::path abs_datadir{fs::absolute(argv[1])};
+    fs::create_directories(abs_datadir);
 
 
     // SETUP: Context