Review checkboxes and radio attr/prop usage

[tadatuta]

It turned out that form.reset() works wrong with current way of checking/unchecking checkboxes.

Such variant was introduced in https://github.com/bem/bem-components/commit/012de48146234dc5c1ea47297687046311a0ac6b as a fix for previous change made for a11y: https://github.com/bem/bem-components/commit/db4a1385029ee328550aaacb541b41e021381fea

Is there any way to satisfy a11y and get rid of attr() setter?

[tadatuta]

cc @aristov

[narqo]

According to WAI-ARIA Authoring Practices for Checkbox widget, it should be possible to use aria-checked attribute.