Add support for detecting Keyboard backlight using sysfs node

Add new light type for Keyboard backlight and corresponding
detection logic. Also, refactor PeripheralController logic to
support Light type and light capabilities similar to how it is
handled on Java side of code.

Test: atest inputflinger_tests
Bug: 245506418
Change-Id: Ic69e42555bf57a66683fcf359169869ee2a00749