Add logging for IAudioProcessor::process()

This is super verbose, but I'm sure it's going to be useful at some
point.

src/common/serialization/vst3/parameter-changes.h

@@ -45,6 +45,12 @@ class YaParameterChanges : public Steinberg::Vst::IParameterChanges {
 
     DECLARE_FUNKNOWN_METHODS
 
+    /**
+     * Return the number of parameter we have parameter change queues for. Used
+     * in debug logs.
+     */
+    size_t num_parameters() const;
+
     /**
      * Write these changes back to an output parameter changes queue on the
      * `ProcessData` object provided by the host.