Settings: add logpersist selection (strings)

(cherry picked from commit 954ed57091a6471f1873c9954fbb16a4f65a25b5)

Strings for selecting between Off, All and All minus radio to
store logs persistently on the local eMMC device. Strings for
warning button when erasing logpersist data.

Bug: 28813587
Bug: 28936216
Change-Id: I3aaa59a6ebbe1a695490b4a72cad2c807c048985