bug: ion-checkbox is toggled by ion-item click

# Bug Report

**Ionic version:**

[x] **4.x**

**Current behavior:**

If you have the following markup, any click or tap on the ion-item will toggle the ion-checkbox:

```

```

**Expected behavior:**

The ion-checkbox should only toggle when it is clicked, or the click event from the ion-item should be cancellable.

**Steps to reproduce:**

**Related code:**

[Codepen](https://codepen.io/bsbechtel/pen/YzXWKOW?editors=1100)

**Other information:**

This issue has been brought up multiple times and not fixed: [19590](https://github.com/ionic-team/ionic/issues/19590) [15850](https://github.com/ionic-team/ionic/issues/15850) [17832](https://github.com/ionic-team/ionic/issues/17832)

**Ionic info:**

```
insert the output from ionic info here
```