Verify output audio sample rate.

Check that the sample rate of the audio format in the output file matches the
expected sample rate, taking into account spectral band replication (SBR) which
halves the sample rate in the header.

All tests verify the output audio at the moment, but new tests can be added
later where the functionality is disabled (in order to make other verifications
independently).

Copied from ag/407162.

Bug: 11819504
Change-Id: Ieec9fe253c1abb36bece725f6c8d3aea9c2f515f