refactor: replace boost::filesystem with std::filesystem

Warning: Replacing fs::system_complete calls with fs::absolute calls
in this commit may cause minor changes in behaviour because fs::absolute
no longer strips trailing slashes; however these changes are believed to
be safe.

Co-authored-by: Russell Yanofsky <russ@yanofsky.org>
Co-authored-by: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>

src/util/settings.cpp

@@ -2,11 +2,17 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#include <fs.h>
 #include <util/settings.h>
 
 #include <tinyformat.h>
 #include <univalue.h>
 
+#include <fstream>
+#include <map>
+#include <string>
+#include <vector>
+
 namespace util {
 namespace {
 
@@ -63,7 +69,7 @@ bool ReadSettings(const fs::path& path, std::map<std::string, SettingsValue>& va
     // Ok for file to not exist
     if (!fs::exists(path)) return true;
 
-    fsbridge::ifstream file;
+    std::ifstream file;
     file.open(path);
     if (!file.is_open()) {
       errors.emplace_back(strprintf("%s. Please check permissions.", fs::PathToString(path)));
@@ -106,7 +112,7 @@ bool WriteSettings(const fs::path& path,
     for (const auto& value : values) {
         out.__pushKV(value.first, value.second);
     }
-    fsbridge::ofstream file;
+    std::ofstream file;
     file.open(path);
     if (file.fail()) {
         errors.emplace_back(strprintf("Error: Unable to open settings file %s for writing", fs::PathToString(path)));