inputflinger_tests: Add input reader tracing test

This checks the very basic evdev-level tracing added so far, taking
inspiration from InputReaderIntegrationTest to use a uinput device to
send some events, then checking they appear in the trace.

Bug: 394861376
Test: $ atest inputflinger_tests
Flag: TEST_ONLY
Change-Id: I80e3ceef7c858035fbb20f615610384b92b40bc5