Simplify IMMS#startInputOrWindowGainedFocusInternal() part 4/5

This is a series of CLs to reduce the average indentation level of
InputMethodManagerService#startInputOrWindowGainedFocusInternal().

With this CL, InputMethodManagerService.java imports
android.view.WindowManager.LayoutParams instead of
android.view.WindowManager.

This is a mechanical refactoring.  There should be no behavior change.

Bug: 34886274
Test: atest CtsInputMethodTestCases CtsInputMethodServiceHostTestCases
Change-Id: I730a8cb93167f2894c073ea6e3620d49f06c7600