Changes to lockscreen for laying out the 6 digit view

This CL aims at making changes for laying out the 6 and non 6 digit PIN
view, and also the logic for unlocking automatically after a user sets a
6 digit PIN.

Test: Tested by building and flashing on local
Bug: b/262935304
Change-Id: Ic9bde6d1572a30bbc1c03164b93c4292ca4318d3