Include inputViewShown in verifyInputViewStatus

Currently verifyInputViewStatus includes a few checks, but does not
incldue checking isInputViewShown. This refactors the method to also
check this value, to reduce duplication.

Additionally re-orders the methods in TestActivity and
InputMethodServiceWrapper, as well as storing the static instance of the
wrapper in a weak reference.

Flag: EXEMPT testfix
Bug: 394328311
Test: atest InputMethodServiceTest
Change-Id: Idd844caadedec49b0165d3cf4ed6ca3e61638783