Refactor package structure for scalability and resolve lint problems.

This change only refactor package structure without
changing any logic and resolve Kotlin list problems.

Test: atest -v CtsNearbyMultiDevicesTestSuite
Bug: 214015364
Ignore-AOSP-First: nearby_not_in_aosp_yet
Change-Id: Ic0b7c374e22891c2c4f494c0a617cba7f253e8de
6 files changed