Ensure I/O buffers in libufs(3) are 128-byte aligned.

Various disk controllers require their buffers to be aligned to a
cache-line size (128 bytes). For buffers allocated in structures,
ensure that they are 128-byte aligned. Use aligned_malloc to allocate
memory to ensure that the returned memory is 128-byte aligned.

While we are here, we replace the dynamically allocated inode buffer
with a buffer allocated in the uufsd structure just as the superblock
and cylinder group buffers do.

This can be removed if/when the kernel is fixed. Because this problem
has existed on one I/O subsystem or another since the 1990's, we
are probably stuck with dealing with it forever.

The problem most recent showed up in Azure, see:

https://reviews.freebsd.org/D41728
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=267654

Before these fixes were applied, it was confirmed that the changes
in this commit also fixed the issue in Azure.

Reviewed-by: Warner Losh, kib
Tested-by: Souradeep Chakrabarti of Microsoft (earlier version)
PR: 267654
Differential Revision: https://reviews.freebsd.org/D41724