Bump version code and name to Dialer v12

This CL bumps the version name of Dialer from Dialer v11 to Dialer v12. This CL
also bumps the version code from 15***** to 1600000.

I've also set 'version_conf_incrementer_max_version_code' at go/dialer-v11
to 1599999.

Test: N/A
PiperOrigin-RevId: 161418347
Change-Id: I961f22481d813d66b950894b3783e13624de733e