Changed widget picker personal-work tab layout

Used layout margin instead of padding. Also making sure that Talkback would focus on the widgets title once the widget picker is opened.

Before: https://screenshot.googleplex.com/AgZspqTc7yS2Lte
Now: https://screenshot.googleplex.com/5W66ky7XAByCFRZ

Fix: 247121867
Test: Manual
Change-Id: I76534454754c5e57ab51ae7ce06ca4370a3fd22b