pipewire will allocate buffers aligned to the max alignment required for
the CPU. Take this into account and don't expect larger alignment.
Fixes a warning in mixer-dsp when the CPU max alignment is 16 but the
plugin requires 32 bytes alignment for the AVX2 path (that would never
be chosen on the CPU).
See #2074
Move floatmix to the audiomixer plugin and change the name to
AUDIO_MIXER_DSP.
Add runtime selectable sse and sse2 optimizations.
Load the port mixer plugin dynamically based on the factory_name.
Add some more debug
