Focus on search field EditText and launch keyboard when AutoComplete is opened

This ticket is to track @jollygreenegiant's question/request (https://github.com/mapbox/mapbox-plugins-android/issues/1008#issuecomment-510541027) regarding making the search field focused when the autocomplete activity is launched so that they keyboard automatically comes up, rather than the user having to click in the box first.

Start by locating the autocomplete activity and its search-field EditText in the Android plugin. Check how the activity opens and verify that the field receives focus and the keyboard appears automatically when autocomplete launches; confirm that users can still search normally.

Written by the indexing model from the issue text.