Existence of ‘number’ Key in `Options.arrays` Changes Parsing

The documentation says to set numbers: true to parse option-array values as numbers. However, this value can be anything other than true and yargs will still use number parsing. This is particularly confusing when trying to set numbers: false or numbers: undefined.

> const parser = require('yargs-parser')
undefined
> parser('--foo dog cat', {array: {key: 'foo'}})
{ _: [], foo: [ 'dog', 'cat' ] }
> parser('--foo dog cat', {array: {key: 'foo', number: false}})
{ _: [], foo: [ NaN, NaN ] }
> parser('--foo dog cat', {array: {key: 'foo', number: undefined}})
{ _: [], foo: [ NaN, NaN ] } 

This applies to boolean as well.

Start with the option-array parsing behavior described in the issue and compare it with the parser options documentation. Reproduce the examples for array.number and array.boolean, then trace how the presence of those keys is interpreted. Done means false or undefined no longer enables the corresponding type conversion, with the documented behavior preserved.