[FASTFAT] Don't mix FileNameInformation and FileNamesInformation (and support the...

This commit fixes weird behavior in our FastFAT implementation. It was mixing two classes:
FileNameInformation and FileNamesInformation. It was handling FileNameInformation like
FileNamesInformation and was filling buffer with FILE_NAMES_INFORMATION structure instead
of FILE_NAME_INFORMATION structure (how many things did that break?!).
Also, it wasn't implementing the FileNamesInformation class at all. This is required by
ntdll_winetest:directory which doesn't expect it to fail and thus, attempts to read
never filled in memory.

This commit fixes the winetest crash, and may fix other weird FS behavior.

CORE-13367