modules: move softdsp-endpoint inside module-pipewire

modules/meson.build

modules/module-pipewire.c

modules/module-pipewire/audio-softdsp-endpoint.c

modules/module-pipewire/audio-softdsp-endpoint/adapter.c

modules/module-pipewire/audio-softdsp-endpoint/adapter.h

modules/module-pipewire/audio-softdsp-endpoint/convert.c

modules/module-pipewire/audio-softdsp-endpoint/convert.h

modules/module-pipewire/audio-softdsp-endpoint/stream.c

modules/module-pipewire/audio-softdsp-endpoint/stream.h

src/wireplumber.conf