(test/gurka/) Using C++17 filesystem with few changes

[cvvergara]

Issue

What issue is this PR targeting? If there is no issue that addresses the problem, please open a corresponding issue and link it here.

Tasklist

• include "filesystem.h" -> #include <filesystem>
  • filesystem::fn -> std::filesystem::fn
  • On 5 files that do not have warnings
  • Added #include <filesystem> when needed
• Add tests
• Add #fixes with the issue number that this PR addresses
• Update the docs with any new request parameters or changes to behavior described
• Update the changelog
• If you made changes to the lua files, update the taginfo too.

Requirements / Relations

Link any requirements here. Other pull requests this PR is based on?

[nilsnolde]

LGTM thanks!