selftests/proc: add /proc/pid/smaps tearing tests

selftests/proc: add /proc/pid/smaps tearing tests

Add tearing tests for /proc/pid/smaps file.  New tests reuse the same
logic as with maps file but skipping all the data except for the VMA
addresses, which are the only part relevant for the tearing tests.  Skip
PROCMAP_QUERY parts of the tests because smaps does not implement that
ioctl.

Link: https://lore.kernel.org/20260426062718.1238437-4-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Liam R. Howlett <liam@infradead.org>
Cc: Jann Horn <jannh@google.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>