Switch GnssTimeUpdateService to internal service

Switch GnssTimeUpdateService to calling TimeDetectorInternal, not
TimeDetectorService over AIDL.

TimeDetectorInternal was recently added for NetworkTimeUpdateService and
this commit follows the same pattern.

Bug: 219693030
Bug: 222295093
Test: atest services/tests/servicestests/src/com/android/server/timedetector/
Test: atest services/tests/servicestests/src/com/android/server/timezonedetector/
Test: atest core/tests/coretests/src/android/app/timedetector/
Change-Id: I916cf878469280e6c9498baf2cf930e140c3a386