CVE-2026-10671 User thread can re-initialize an in-use `k_pipe`, corrupting kernel wait queues (`CONFIG_USERSPACE`)

In Zephyr's kernel pipe implementation, the userspace syscall verifier zvrfykpipeinit in kernel/pipe.c used KSYSCALLOBJ which requires the kernel object to already be initialized instead of KSYSCALLOBJNEVERINIT which rejects an already-initialized object. As a result, on CONFIGUSERSPACE builds an...