Add 16dp between nav bar and container by setting extra padding to the recyclerView.

bug:298593161
Test: manual:
(Adjusting bottom padding of recyclerView):
3button nav after closed: https://drive.google.com/file/d/1xTXtzOC-n3_vGXs34FjL_52jiY60piAA/view?usp=sharing
3button nav after opened: https://drive.google.com/file/d/1xS4Wu41-4ogYzVRh1UxDW39DZW214vSz/view?usp=sharing
gesture nav after closed: https://drive.google.com/file/d/1xQGL-Qi5sGwWqQsOLQAsvxpNlJGklBSg/view?usp=sharing
gesture nav after opened: https://drive.google.com/file/d/1xQ9YNUv89RsT9Tsa85BlEt64twDHk-l6/view?usp=sharing

(USING DIVIDER METHOD):
3button nav after closed: https://drive.google.com/file/d/1YG1pFmU4023-wO2okC_wkwsW5L8IUTkl/view?usp=sharing
3button nav after opened: https://drive.google.com/file/d/1YCBIqzFkxNH9fNuE0o2YTz_221ZRAmSA/view?usp=sharing
gesture nav after closed: https://drive.google.com/file/d/1YIBRglQk6SsSe7_nbggcQZBE7aERGT74/view?usp=sharing
gesture nav after opened: https://drive.google.com/file/d/1YGzbgQPRFKhuSZ95BF6fx_8NfPyocCxN/view?usp=sharing
Flag: ACONFIG com.android.launcher3.Flags.enable_private_space

Change-Id: Ibfd4896c1477b3e498389d6451ca458a01d98952