Move network time logic out of AlarmManagerService

Move network time logic out of AlarmManagerService in preparation for
a future refactoring. The TimeDetectorService is now a better home for
functionality associated with time signals, as it should receive most
time signals from various sources so it can determine whether the
device's system clock needs to change.

Although the TimeDetectorService is not currently informed every time
the NtpTrustedTime obtains a new time, it should be in future after
further work in later commits.

This change modifies the logic in SystemClock to match the GNSS time
logic in the same class, i.e. rather than calculating the "current time"
in the system server and then sending it over binder (introducing a
delay), the latest information needed to compute the time is sent to the
client, which then calculates the current time.

Bug: 219693030
Bug: 222295093
Test: atest services/tests/servicestests/src/com/android/server/timedetector/TimeDetectorServiceTest.java
Test: atest cts/tests/tests/os/src/android/os/cts/SystemClockSntpTest.java
Test: Treehugger
Change-Id: I80ea52877352122b52ac54daed8b092f3cc18e02