libgui: Add test for OOB slot number in dequeue

Adds a unit test that verifies that a malicious BnGraphicBufferProducer
cannot pass an invalid slot number to a Surface and thus cause the
Surface to segfault (or otherwise access out-of-bounds memory).

Bug: 36991414
Test: The new Malicious* tests pass after applying the security patch
Change-Id: I2083465a496cfcc8e8c3b3bc288f5f6904005ac3