Refactor to abandon “input object” approach

[zhusee2]

There are 3 components left using a previous “input object”, which explicitly expects an input prop to pass all input-related props to their inner <input>. They are:

• <Checkbox>
• <SearchInput>
• <Switch>

As their main purpose is to act as real inputs with custom appearance, they should take all unknown props as input props by default.