sync: add `sync.thread_id() u64 {` (#13810)

vlib/sync/thread_default.c.v

@@ -0,0 +1,7 @@
+module sync
+
+fn C.pthread_self() usize
+
+pub fn thread_id() u64 {
+	return u64(C.pthread_self())
+}

vlib/sync/thread_test.v

@@ -0,0 +1,22 @@
+import sync
+
+fn simple_thread() u64 {
+	tid := sync.thread_id()
+	eprintln('simple_thread thread_id: $tid.hex()')
+	return tid
+}
+
+fn test_sync_thread_id() {
+	mtid := sync.thread_id()
+	eprintln('main thread_id: $sync.thread_id().hex()')
+	x := go simple_thread()
+	y := go simple_thread()
+	xtid := x.wait()
+	ytid := y.wait()
+	eprintln('main thread_id: $sync.thread_id().hex()')
+	dump(xtid.hex())
+	dump(ytid.hex())
+	assert mtid != xtid
+	assert mtid != ytid
+	assert xtid != ytid
+}

vlib/sync/thread_windows.c.v

@@ -0,0 +1,7 @@
+module sync
+
+fn C.GetCurrentThreadId() u32
+
+pub fn thread_id() u64 {
+	return u64(C.GetCurrentThreadId())
+}