Allow the original content insets to be set after setting up the keyboard observer

[farochocolom]

Came across a case where we needed to set the insets in a viewDidLayoutSubviews() and we were setting the originalContentInset on the setupKeyboardObservers() which is convention to call on viewWillAppear().
Since viewWillAppear()gets called before viewDidLayoutSubviews(), we were setting this to nil:
keyboardScrollableScrollView?.originalContentInset = keyboardScrollableScrollView?.contentInset

This change sets the originalContentInset only when we prompt the keyboard to show and only does if we haven't set it before, or keyboardScrollableScrollView?.originalContentInset == nil

Also bumped up the deployment target but that can be reverted if necessary

[CLAassistant]

All committers have signed the CLA.

[wmcginty]

I think this needs to be a major version upgrade if we're dropping iOS versions, but 👍 for me.

[wmcginty]

@Specialist17 It looks like there's an issue with running the tests that needs to be looked at, and a Changelog.md entry added for the change.

[tylermilner]

Is this necessary for some piece of functionality in the iOS 11+ SDK? I would rather us leave the deployment target alone unless there is a good reason to bump it up.

[wmcginty]

I think it's the use of adjustedContentInset instead of contentInset, but I'm not sure if that's required as part of the fix - or if just moving the setting of the variable to the first keyboard observing would do it.

[tylermilner]

Thanks, @wmcginty I didn't notice the use of adjustedContentInset, but that does seem to be iOS 11+ only. @Specialist17 was it intentional to use adjustedContentInset or was the moving of the code and the nil check the main fix you were trying to do here?

if self?.keyboardScrollableScrollView?.originalContentInset == nil {
    self?.keyboardScrollableScrollView?.originalContentInset = self?.keyboardScrollableScrollView?.contentInset
}

[farochocolom]

@tylermilner the moving of the code and the nil check was the main idea here. I'll revert the deployment target change

[wmcginty]

@Specialist17 Looks like we just need a Changelog entry, and we're good to go!