NonBooleanPropertyPrefixedWithIs: Allow boolean functions

[brittanyberlanga]

This change builds on top of #4684 which allowed functions with a boolean return type to comply with the NonBooleanPropertyPrefixedWithIs rule. That change only allowed functions with zero parameters. With this change, I’m proposing that we open up the exception to any function with a boolean return type.

For example, something like the following would be considered compliant.

interface Business {
    val isOpenAt: (DateTime) -> Boolean
}

Let me know if there are any reservations around this change. My team found that it was odd that there was this limitation and I thought I’d check out if you all agree as well.

[schalkms]

Thank you for this awesome contribution! 🙂