This commit creates a textfield package for resources related to text fields. It does not move TextInputLayout to this package, since that would break current users.
There's a small unrelated change included in this move: drawable-v21/design_bottom_navigation_item.xml was not moved along with its compat counterpart when it was moved recently, so I moved it while I was moving things around.
PiperOrigin-RevId: 183101110
