[FIX] web: checkbox readonly is RO in list editable

Since f4fbaf1e the structure of checkboxes has been improved, now we
have something like:

```
 <input type="checkbox" id="checkbox-18" class="custom-control-input">
 <label for="checkbox-18" class="custom-control-label">&#8203;</label>
```

With the first input invisible (whilst before it was visible and the
clickable element).

This cause an issue in an editable list view:

- we have a boolean readonly field in a cell
- we are on focused on a line (not in the boolean field cell)
- we click on the boolean field

=> the check mark is toggled

This is because when we switch cell, we try to activate the widget of
the other cell. Before f4fbaf1e this issue did not happen since the
browser do not generate a click event when clicking a disabled checkbox.

With this changeset, a disabled FieldBoolean is not focusable as is the
case for other fields, so we can't "activate" it.

Without the fix, the added test fails with:

 [clicking disabled checkbox did not work]

opw-1958433
closes #32652

Signed-off-by: Aaron Bohy (aab) <aab@odoo.com>