Move up caller's display and window validation

This CL is a preparation for FocusController. It moves up the caller's
display and window parameters validation. This refactoring will
make the startInput logic move to FocusController easier.

This is just a refactoring CL, no behavior change is expected.

Bug: 314149476
Test: atest CtsInputMethodTestCases FrameworksServicesTests

Change-Id: Icd4095f9ce501c8cf0b1f4862a9c95050df7dc73