Make PeopleActivity extends AppCompatActivity (1/3)

This CL includes a subset of reversion of ag/871001.

This topic of CLs will lead to the following changes in APK sizes:

- GoogleContacts: 8.0MB --> 8.7MB
- GoogleContacts-N: 7.6MB --> 8.2MB

Bug 27687799

Change-Id: Id94598e42a5016badeafee3f4f0dc2a515fc68eb