Use std filesystem (#3284)

* Use std::filesystem for path names and impl

tests/includes.h

@@ -31,3 +31,8 @@
 #include "spdlog/sinks/null_sink.h"
 #include "spdlog/sinks/stdout_color_sinks.h"
 #include "spdlog/spdlog.h"
+
+// to_string_view
+[[nodiscard]] constexpr spdlog::string_view_t to_string_view(const spdlog::memory_buf_t &buf) noexcept {
+    return spdlog::string_view_t{buf.data(), buf.size()};
+}