allow showing all elements on ios page command

[bootstraponline]

apparently people want to show all elements instead of only visible elements, this should be easy to add as an optional arg to the ios page command.

[cyrilchampier]

It would indeed allow to write tests in command line instead of avoid to launch the "inspector" to understand the hierarchy of a page.

[KazuCocoa]

We can get all elements include hidden view via predicate with the following method.

ruby_lib/lib/appium_lib/ios/helper.rb

Line 336 in 2ff78b1

def find_eles_by_predicate_include(class_name: '*', value:)

I think we can get all element via page with predicate.
https://github.com/appium/ruby_lib/blob/master/lib/appium_lib/ios/helper.rb#L139