libzpool: set thread names

Arrange for the thread/task name to be set when new threads are created.
This makes them visible in the process table etc.

pthread_setname_np() is generally available in glibc, musl and FreeBSD,
so no test is required.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Sponsored-by: https://despairlabs.com/sponsor/
Closes #16140

lib/libzpool/kernel.c

@@ -92,7 +92,8 @@ zk_thread_wrapper(void *arg)
 }
 
 kthread_t *
-zk_thread_create(void (*func)(void *), void *arg, size_t stksize, int state)
+zk_thread_create(const char *name, void (*func)(void *), void *arg,
+    size_t stksize, int state)
 {
 	pthread_attr_t attr;
 	pthread_t tid;
@@ -140,6 +141,8 @@ zk_thread_create(void (*func)(void *), void *arg, size_t stksize, int state)
 	VERIFY0(pthread_create(&tid, &attr, zk_thread_wrapper, ztw));
 	VERIFY0(pthread_attr_destroy(&attr));
 
+	pthread_setname_np(tid, name);
+
 	return ((void *)(uintptr_t)tid);
 }