Accept List<> instead of ArrayList<> around InputMethodListBuilder

InputMethodListBuilder can actually take

  List<InputMethodInfo>

instead of

  ArrayList<InputMethodInfo>,

and such a change will help us merge the following fields

  InputMethodManagerService#mMethodList
  InputMethodManagerService#mMethodMap

into

  InputMethodManagerService#mSettings

in a subsequent CL.

There must be no observable behavior change.

Bug: 309837937
Bug: 309870347
Test: presubmit
Change-Id: Ie81ad03693c91d8f39167c0711649b5f2448ceb9