VIMS: Don't set recognizer when assistant changes.

Decoupling recognizer from assistant allows it to be provided by a
different package.
The recognizer is now set only on initializing the user or when
packages are modified.

There should be no change to how the assistant or interactor is set.

Bug: 167597525
Test: manual - set/unset assistant, reboot.
Test: atest CtsVoiceInteractionTestCases
Change-Id: I42bd1ab768070d444a1f6e3e78571cae8288a8ba