bpo-26185: Fix repr() on empty ZipInfo object (#13441)

* bpo-26185: Fix repr() on empty ZipInfo object

It was failing on AttributeError due to inexistant
but required attributes file_size and compress_size.
They are now initialized to 0 in ZipInfo.__init__().

* Remove useless hasattr() in ZipInfo._open_to_write()

* Completely remove file_size setting in _open_to_write().