ALGORITHMS: Clean KissFFT wrapper processing method

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
TESTS: Minor naming/comment fixes

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
TESTS: Moved common test sampling freq to common test header

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
TESTS: Fix ambiguous equality cases

Now allowing descriptor output to be equal to the given meta extremum.

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
DESCRIPTORS: All descriptors now using the same tests

Signed-off-by: Gama <misept.dieseneuf@gmail.com>
ALGORITHMS: Minor style fixes

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