debugobjects: Refill per CPU pool more agressively

Right now the per CPU pools are only refilled when they become
empty. That's suboptimal especially when there are still non-freed objects
in the to free list.

Check whether an allocation from the per CPU pool emptied a batch and try
to allocate from the free pool if that still has objects available.

   	    kmem_cache_alloc()	kmem_cache_free()
Baseline:   295k		245k
Refill:	    225k		173k

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com>
Link: https://lore.kernel.org/all/20241007164914.439053085@linutronix.de