// Within each goroutine, regions must nest. That is, regions started
// after this region must be ended before this region can be ended.
// Recommended usage is
//
//	defer trace.StartRegion(ctx, "myTracedRegion").End()
func StartRegion(ctx context.Context, regionType string) *Region {
	if !IsEnabled() {
		return noopRegion
	}
	id := fromContext(ctx).id
	userRegion(id, regionStartCode, regionType)