Don't initialize the People Service at boot but on demand.

The service is not used by any known apps and we don't used any of it's  data.

By making the service lazy, we may gain some ms at boot and still preserve its functionality.

Note that the associated PeopleServiceTest.java had to be modified slightly because of a bug with the test itself. The test was not emulating the change to the boot phase and therefore it was not running the full initialization of the service. Making it lazy, forces the test to comply.

Test: Run the unchanged CTS test with `atest android.app.people.cts.PeopleManagerTest` and `atest com.android.server.people.PeopleServiceTest`x

Skip-CP-To-Master: We need to look at a different strategy for master https://b.corp.google.com/issues/286193387

Bug: 285828603
Bug: 286193387
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:062eda268fa33bee3364931b9b6eb293af5f718b)
Merged-In: I1db9446dbcabd7f9e8b1fdc0390b021f1e0185fa
Change-Id: I1db9446dbcabd7f9e8b1fdc0390b021f1e0185fa