Reset TSMS when the device is unlocked.

This ports my previous CL for InputMethodManagerService [1] to
TextServicesSettings (TSMS).

With File-Based Encryption (FBE), now we have yet another runteime event
to reset TSMS state in order to keep the list of available spell
checkers updated.

See my previous commit message [1] for details about the idea.

Rebuild spell checker list when the system becomes ready.

  [1]: Ifa2225070bf8223f8964cf063c86889e312c5e9a
       0e367d08aab2c1cb2d0fb9cbf1e8a6d09d1ac523

Bug: 27456430
Change-Id: I2b5a6989a99fd18b3bf109f5cda6270ccadaaf6d