cpuset: Byte swap cpuset for compat32 on big endian architectures

Summary:
BITSET uses long as its basic underlying type, which is dependent on the
compile type, meaning on 32-bit builds the basic type is 32 bits, but on
64-bit builds it's 64 bits. On little endian architectures this doesn't
matter, because the LSB is always at the low bit, so the words get
effectively concatenated moving between 32-bit and 64-bit, but on
big-endian architectures it throws a wrench in, as setting bit 0 in
32-bit mode is equivalent to setting bit 32 in 64-bit mode. To
demonstrate:

32-bit mode:

BIT_SET(foo, 0): 0x00000001

64-bit sees: 0x0000000100000000

cpuset is the only system interface that uses bitsets, so solve this
by swapping the integer sub-components at the copyin/copyout points.

Reviewed by: kib
Sponsored by: Juniper Networks, Inc.
Differential Revision: https://reviews.freebsd.org/D35225

(cherry picked from commit 47a57144af25a7bd768b29272d50a36fdf2874ba)

Fix the build after 47a57144

(cherry picked from commit 89737eb8290a10d96b77afac1b68e4740b43353b)

cpuset: Fix the KASAN and KMSAN builds

Rename the "copyin" and "copyout" fields of struct cpuset_copy_cb to
something less generic, since sanitizers define interceptors for
copyin() and copyout() using #define.

Reported by: syzbot+2db5d644097fc698fb6f@syzkaller.appspotmail.com
Fixes: 47a57144af25 ("cpuset: Byte swap cpuset for compat32 on big endian architectures")
Sponsored by: The FreeBSD Foundation

(cherry picked from commit 4a3e51335e86cee02569c04b9f1e95ca9abcb170)

Use Linux semantics for the thread affinity syscalls.

Linux has more tolerant checks of the user supplied cpuset_t's.

Minimum cpuset_t size that the Linux kernel permits in case of
getaffinity() is the maximum CPU id, present in the system / NBBY,
the maximum size is not limited.
For setaffinity(), Linux does not limit the size of the user-provided
cpuset_t, internally using only the meaningful part of the set, where
the upper bound is the maximum CPU id, present in the system, no larger
than the size of the kernel cpuset_t.
Unlike FreeBSD, Linux ignores high bits if set in the setaffinity(),
so clear it in the sched_setaffinity() and Linuxulator itself.

Reviewed by: Pau Amma (man pages)
In collaboration with: jhb
Differential revision: https://reviews.freebsd.org/D34849
MFC after: 2 weeks

(cherry picked from commit f35093f8d6d8155ab2e56c11ee03d474688b16a2)