Refine Style/Grid picker recyclerview layout

 - Fix recyclerview's items not center aligned issue
 Before:
 https://screenshot.googleplex.com/7L8Q9hFDdeL.png
 https://screenshot.googleplex.com/ih5Ad7vxAeS.png
 After:
 https://screenshot.googleplex.com/8JFtHwvjy7s.png
 https://screenshot.googleplex.com/M9vjZrwdOik.png

 Bug: 160753361
 Test: manually, please check the screenshots

Change-Id: Icc277713571abda8d4537a8e6c09689445aba61c