* Click next moves the focus to next focusable textfield
Fixes https://github.com/NativeScript/NativeScript/issues/5033
When clicking next arrow on the virtual keyboard we were returning true which means we handled the event so the OS doesn't move the focus to the next item. This PR delete the `return true` when the action is `IME_ACTION_NEXT` so that next focusable item is automatically focued
* Fix IME_ACTION_PREVIOUS to raise returnPress event.
Added unit-test that IME_ACTION_PREVIOUS to raise returnPress event.
Refactored text-field-tests