Foundation: deprecate Poco functionality that is provided with std::filesystem

[matejk]

Poco libraries implement some functionality that is provided with std::filesystem.

Minimum standard that Poco supports is C++17 and that includes std::filesystem.

Redundant Poco functionality shall be deprecated or rewritten using std::filesystem features.

• Poco::DirectoryIterator
• Poco::File
• Poco::Path

[obiltschnig]

Probably not entirely feasible, as I'm pretty sure that Poco can do things that std::filesystem cannot do. Specifically, the UTF16 <> UTF8 conversion Poco does on Windows.

See also: Poco::Thread and std::thread for how things went ;-)

[matejk]

Poco implementation could use std::filesystem internally as it is the case with Optional?

[obiltschnig]

The main problem could be that std::filesystem lacks features that Poco::File, etc. support.