internal/task: swap stack chain when switching goroutines

This change swaps the stack chain when switching goroutines, ensuring that the chain is maintained consistently.
This is only really currently necessary with asyncify on wasm.

src/internal/task/task_asyncify.go

@@ -104,6 +104,7 @@ func (*stackState) unwind()
 func (t *Task) Resume() {
 	// The current task must be saved and restored because this can nest on WASM with JS.
 	prevTask := currentTask
+	t.gcData.swap()
 	currentTask = t
 	if !t.state.launched {
 		t.state.launch()
@@ -112,6 +113,7 @@ func (t *Task) Resume() {
 		t.state.rewind()
 	}
 	currentTask = prevTask
+	t.gcData.swap()
 	if t.state.asyncifysp > t.state.csp {
 		runtimePanic("stack overflow")
 	}