dynamic_sensor: Add stubbed sensor multi-HAL 2.1 support.

Bug: 195964858
Test: Verified the dynamic sensor sub-HAL initializes and non-dynamic
 sensors can sample.
Test: See details in testing done comment in
 https://googleplex-android-review.git.corp.google.com/15806307 .
Change-Id: I59934814cc61c7319731eb840ff2132a8c5ce241
3 files changed