Add config to override face unlock bypass setting

Introduces a config parameter that can be used to override the setting
for whether successfully authenticating with face auth should dismiss
keyguard. This is intended for testing only.

Test: For each config setting (0, 1, 2), do the following:
1. Toggle on "Settings > Security > Face unlock > Skip lock screen"
2. Lock the device and authenticate using face
3. Repeat steps with "Skip lock screen" toggled off

Bug: 184995230
Change-Id: I95697d3a611f134efe36330291570e5e5b10ff12