Allow focusing TextInput when already focused

Summary:
Right now, `requestFocus()` is a no-op if the EditText view thinks it's already focused. In certain cases, though, we still want to focus the view even if it's already focused - for example, if TalkBack is enabled and you dismiss the keyboard, you want to be able to tap on the TextInput again to bring back the keyboard, even though the View never thinks it lost focus.

What I'm doing instead is basically disregarding the View's current focus state if we *would* focus the TextInput, which is in 3 circumstances:

- When the view is attached to a window, if autofocus is true
- When the focus is being requested by JS
- When the focus is being requested by an accessibility action from the OS

Changelog: [Android][Fixed] Change how TextInput responds to requestFocus to fix a11y focus issue

Reviewed By: mdvacca

Differential Revision: D19750312

fbshipit-source-id: 30b9fab40af4a083fa98f57aba7e586540238bea