Add inputflinger InputReader fuzzer

This CL aims to add a fuzzer to test inputflinger's InputReader
functionality.

Test: Fuzzers tested on a Pixel 3a, and run for approximately 1M
      iterations each to test stability. Executions/sec vary from
      ~400-900, depending on the fuzzer.

Summary of updates:

Coverage improvements: 36.75% to 82.29%

Design changes:
[1] Provided a mock Implementation for InputReaderInterface and
    added support for newer APIs.
[2] Enabled support for few more Events that helped in discovering
    new code paths.
[3] Added missing APIs and resolved OOB Access crashes.
[4] Refactored InputReaderFuzzer to resolve build errors.

Signed-off-by: Michael Ensing <michael.ensing@leviathansecurity.com>
Change-Id: I8e9c5f78960dba6d84a46ad7ee46963b3be79fec