CVE-2026-72436: netfilter: ipset: Don't use test_bit() in lockless RCU readers in hash types

In the Linux kernel, the following vulnerability has been resolved:

netfilter: ipset: Don't use testbit() in lockless RCU readers in hash types

Sashiko pointed out that there are a few lockless RCU readers using testbit() which is a relaxed atomic operation and provides no memory barrier guarantees. Use testbitacquire() instead where the operation may run parallel with add/del/gc, i.e. is not one from the next cases

- protected by region lock - in a set destroy phase - in a new/temporary set creation phase