TESTS: Clean various tests variables

Some of them were tests-specific and thus moved into the dedicated test
file, other were useless, comments were missing etc.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
DESCRIPTORS: Add 2 simple tests for AudioWaveform

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
MISC: Fix minor comment typo

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
DESCRIPTORS: Add a simple test for AudioWaveform

Now testing the descriptor output for a constant value signal.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
DESCRIPTORS: Add AudioPower.

Fixes #2.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
TESTS: Remove useless test data

This was actually a debug data set.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>