• Add m_ prefix to the std::FILE member variable
• Add std namespace where possible, to avoid confusion with member functions of the same name.
• Add AutoFile::feof() member function, to be used in place of std::feof(AutoFile::Get())
• Simplify fclose() in terms of release()
• Fix typo in the error message in the ignore member function.

This is a partial backport of core#28060
https://github.com/bitcoin/bitcoin/pull/28060/commits/fa7724bc9d94c08d8facccd0a067d6a3b27fbbc6
Depends on D18982

ninja all check-all