KeyboardInputMapper: Refactor alphabetic keyboard wake unit tests

The mock device for KeyboardInputMapperUnitTest was not an alphabetic
keyboard. Created subclasses with mock alphabetic keyboard and different
flag states to enable test cases for alphabtic and non-alphabetic keyboards
in addition to different flag states.

Test: atest --host inputflinger_tests
Bug: 394280942
Flag: TEST_ONLY
Change-Id: Ia2faf945d3aa3ee138d99a2a2a854006c31c10da