Move TextServicesManagerService to com.android.server.textservices

This CL moves TextServicesManagerService (TSMS)
  from com.android.server
    to com.android.server.textservices
so that we can mechanically factor out inner classes from IMMS to
separate package private classes.

This is purely a mechanical refactoring of an implementation detail.
There should be no observable behavior difference.

Fix: 115516399
Test: manually verified with AOSP spellchecker
Change-Id: Iaaf627e48e3f040795f58e03b1292a991afb82b4