Camera: Set CONTROL_CAPTURE_INTENT to STILL_CAPTURE for reprocessing

The legacy camera API would do this by default for reprocessing capture
requests, but this behavior was not carried over into Camera2.

Bug: 252869710
Test: Ran new CTS test on cuttlefish.
Change-Id: I6414aef8d5fd6726a53a73568a7eda6e2d88e1c5