Return a std::optional from EventHub::getAbsoluteAxisInfo

InputDevice::getAbsoluteAxisInfo will be refactored similarly in a
follow-up.

Test: atest inputflinger_tests
Test: m checkinput
Test: build and run inputflinger_multitouch_input_fuzzer for a while
Bug: 245989146
Flag: EXEMPT refactor
Change-Id: I57de645c889de53c8be0f9f8744a62e92fafdadb