Set the widgets pickers' width to at most 80% of screen width on

large screen devices

Test: Phone: Open the full widgets picker and observe the width of
      the widgets picker fills the device screen width.
      Large screen devices: Open the bottom widgets picker and observe
      the width of the widgets picker only takes at most 80% of the
      devices' screen width.
      Same behavior is observed for bottom widgets picker.
Bug: 186425352
Change-Id: I801b73ea031a290fb6a7295dca826ac91841877e