No longer zero out VST3 audio buffers

Apparently we also never did this for VST2 plugins, so this should be
safe. Filling the vectors with zeroes here had a non-negligible
performance impact according to perf.

CHANGELOG.md

@@ -39,6 +39,10 @@ Versioning](https://semver.org/spec/v2.0.0.html).
   unions yabridge uses to differentiate between single and double precision
   floating point audio buffers, undoing all of our efforts at reusing objects
   and preventing memory allocations in the process.
+- VST3 output audio buffers are no longer zeroed out for the plugin. We did this
+  for VST3 plugins, but not for VST2 plugins. Since not doing this never caused
+  any issues with VST2 plugins it should also be safe to do the same thing for
+  VST3 plugins. This further reduces the overhead of VST3 audio processing.
 - Further optimized VST3 audio processing by preallocating small vectors for
   event and parameter change queues.
 - VST2 audio processing also received the same small vector optimization to get

src/common/serialization/vst3/process-data.cpp

@@ -33,7 +33,7 @@ void YaAudioBusBuffers::clear(int32 sample_size,
             std::get<std::vector<std::vector<double>>>(buffers);
         vector_buffers.resize(num_channels);
         for (size_t i = 0; i < vector_buffers.size(); i++) {
-            vector_buffers[i].assign(num_samples, 0.0);
+            vector_buffers[i].resize(num_samples);
         }
     } else {
         if (!std::holds_alternative<std::vector<std::vector<float>>>(buffers)) {
@@ -44,7 +44,7 @@ void YaAudioBusBuffers::clear(int32 sample_size,
             std::get<std::vector<std::vector<float>>>(buffers);
         vector_buffers.resize(num_channels);
         for (size_t i = 0; i < vector_buffers.size(); i++) {
-            vector_buffers[i].assign(num_samples, 0.0f);
+            vector_buffers[i].resize(num_samples);
         }
     }
 }