[tests] Refactor negative audio tests (efficiency/clarity)

This CL refactors the negative test cases (those that expect
the FIDL object to fail, and the channel to disconnect) to
gather common setup code, and to 'checkerboard' our validation
of the various scenarios to reduce test running time.

Test: build, CQ, git-file-tidy

Change-Id: Ie282a81ad31f6aa3c7e1eb72ccbba8a5a05ed994
6 files changed