Switch to SystemService lifecycle in TSMS.

Like we did this for InputMethodManagerService [1],
TextServicesManagerService (TSMS) needs to be recognized by
SystemServiceManager with SystemService lifecycle mechanism so that we
can receive SystemService#onUnlockUser() event, which is necessary to
make TSMS encryption-aware.

As a preparation, with this CL we only does mechcanical migration to
SystemService lifecycle mechanism in TSMS.  Hence no user-visible
behavior change should occur.

  [1]: Ic17667df60b30e5355b61a3601ad27a000cab3a3
       1e33dc8f

Bug: 27456430
Change-Id: Ib3cc799d384f259b4fa3f5295f2da198df015eb8