This MR supercedes !1895 and !3073 as a solution to bug [#50771](https://bugs.winehq.org/show_bug.cgi?id=50771). Rather than fixing the problem of Wine's inability to modify the attributes of read-only files, this patch set instead implements `FileDispositionInformationEx` which the Msys2 and Cygwin runtime libriries can use to avoid needing to modify attributes.
All the flags of `FileDispositionInformationEx` are implemented with the exception of `FILE_DISPOSITION_FORCE_IMAGE_SECTION_CHECK`.
This MR improves upon !3073 by implementing `FILE_DISPOSITION_POSIX_SEMANTICS` and `FILE_DISPOSITION_ON_CLOSE` where the previous MR only implemented `FILE_DISPOSITION_DELETE` and `FILE_DISPOSITION_IGNORE_READONLY_ATTRIBUTE`.
-- v2: ntdll: Implement FILE_DISPOSITION_POSIX_SEMANTICS server: Replace unlink member of closed_fd with disp_flags ntdll/tests: Add tests for FILE_DISPOSITION_POSIX_SEMANTICS