Add infra for an internal API for time_detector

Add the infrastructure / plumbing for an internal API for time_detector
service. Methods will be added to TimeDetectorInternal in later commits.

Bug: 219693030
Bug: 222295093
Test: atest services/tests/servicestests/src/com/android/server/timedetector/TimeDetectorInternalImplTest.java
Test: atest services/tests/servicestests/src/com/android/server/timedetector/TimeDetectorServiceTest.java
Change-Id: I8fd95a2c721432c9d3fa99d6257121e9246b8ab1