Extract HID usage accumulation logic from KeyboardInputMapper

Extract the logic into a HidUsageAccumulator class so that when HID
usage is used in more than one place, the usage code accumulation logic
maintains the same behavior.

There should be no behavior change in this CL.

Bug: 246394583
Test: atest inputflinger_tests
Change-Id: Ia5f9bcac145f07c0d0dca643755dcff1b725d568