slub/kunit: fix a WARNING due to unwrapped __kmalloc_cache_noprof

'modprobe slub_kunit' will have a warning as shown below. The root cause
is that __kmalloc_cache_noprof was directly used, which resulted in no
alloc_tag being allocated. This caused current->alloc_tag to be null,
leading to a warning in alloc_tag_add_check.

Let's add an alloc_hook layer to __kmalloc_cache_noprof specifically
within lib/slub_kunit.c, which is the only user of this internal slub
function outside kmalloc implementation itself.

[58162.947016] WARNING: CPU: 2 PID: 6210 at
./include/linux/alloc_tag.h:125 alloc_tagging_slab_alloc_hook+0x268/0x27c
[58162.957721] Call trace:
[58162.957919]  alloc_tagging_slab_alloc_hook+0x268/0x27c
[58162.958286]  __kmalloc_cache_noprof+0x14c/0x344
[58162.958615]  test_kmalloc_redzone_access+0x50/0x10c [slub_kunit]
[58162.959045]  kunit_try_run_case+0x74/0x184 [kunit]
[58162.959401]  kunit_generic_run_threadfn_adapter+0x2c/0x4c [kunit]
[58162.959841]  kthread+0x10c/0x118
[58162.960093]  ret_from_fork+0x10/0x20
[58162.960363] ---[ end trace 0000000000000000 ]---

Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
Fixes: a0a44d91 ("mm, slab: don't wrap internal functions with alloc_hooks()")
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>