Update Edit Mode Buttons.

This changelist updates the edit mode buttons:
- Updated iconography
- Remove button presence is modal
- Remove button has been centered and filled in.

Test: manual
Fixes: 339667940
Fixes: 330909503
Flag: ACONFIG com.android.systemui.communal_hub TEAMFOOD
Change-Id: I8c19d92533304d3b75a167b2baa47a21eee2cbf9