camera2-portability: Add focus locks and touch-to-focus for API 2

This implements focus locks very simply using only camera2 API requests: the
lens is locked on autoFocus() and unlocked on cancelAutoFocus(), as with the
existing legacy API--backed implementation. Both passive and active focus modes
ares supported, with and without positional focusing.

Change-Id: I26b1866539807fd3d64189923871443056a166af
2 files changed