This PR relaxes the assumed alignment of FILE_BOTH_DIR_INFORMATION in the windows implementation of std.fs.IterabDir.Iterator.next().

I am quite new to zig, so I will happily receive any feedback about how this could be done differently - especially concerning the potential performance penalty of this.

Background

The current windows implementation of std.fs.IterabDir.Iterator.next() makes the assumption that the FILE_BOTH_DIR_INFORMATION struct returned by NtQueryDirectoryFile is aligned properly.

See https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/ntifs/ns-ntifs-_file_both_dir_information

This structure must be aligned on a LONGLONG (8-byte) boundary. If a buffer contains two or more of these structures, the NextEntryOffset value in each entry, except the last, falls on an 8-byte boundary.

However, in practice this is not always guaranteed due to faulty file system drivers, sandboxing tools, or (in my case) endpoint security software.
Currently, this code will panic on the @alignCast() which makes it impossible for the user to work around this issue if it appears.

For context, I found that the same issue appeared in Rust:

• Main issue: std::fs::remove_dir_all occasionally panics on Windows with assertion failed: info.is_aligned() rust-lang/rust#104530
• Firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=1799442
• Sandboxie (apparently triggering this issue in Firefox): Firefox Nightly Crashes (Firefox 108.0a1 64-bit) sandboxie-plus/Sandboxie#2443