2/n: Add setRequestGatekeeperPassword to ChooseLockSettingsHelper

This change adds the plumbing on Settings side for ConfirmLock*.
ChooseLock* will be done in a follow-up CL. The changes in this CL
are not invoked by any code path yet. This will also be integrated
in a follow-up CL.

Bug: 161765592

Perform the following with a local change to use
ChooseLockSettingsHelper#setRequestGatekeeperPassword(true)

Test: GK PW is received when setRequestGatekeeperPassword(true)
Test: GK PW + Challenge sent to GK, GK verifies and caller receives
      GK HAT successfully

Change-Id: Ibd809784b5599343f34836bc5f3e709627b7f22a