Enable WearableSensingService.

This change includes:
1. Enabling WearableSensingManager to be retrievable.
2. Starts WearableSensingService from system server.
3. Introduces WearableSensingShellComamnd for testing.

Bug: 249135378, 244181656
Test: Builds.
Ignore-AOSP-First: to prevent new feature leak.
Change-Id: I4ffaac37c0fe8874ae8b0ae6fec086e4cd27b2f1