Fix VST3 memory leaks

[Quant1um]

I found that when validating the example plugin with ASAN on the wrapper leaks about 2mb of memory. This PR fixes it by:

• Using std::unique_ptr where applicable, and
• Removing result->addRef(); in Vst3Parameter::create. Not sure if it is correct, or what the original purpose of this was, but it seems to work in validator under ASAN, Bitwig and Reaper. Review needed.

Side note: it would probably be a good idea to turn on address sanitizer while validating the plugin in CI

[baconpaul]

I'm pretty sure removing the addRef is wrong, and instead we should add a removeRef when we are done with our parameters explicitly. ASAN in the validator wouldn't necessarily catch this since the validator holds a reference to the param while using it and doesn't try to get it again, as far as I know.

[Quant1um]

I'm pretty sure removing the addRef is wrong, and instead we should add a removeRef when we are done with our parameters explicitly. ASAN in the validator wouldn't necessarily catch this since the validator holds a reference to the param while using it and doesn't try to get it again, as far as I know.

Hmm, it is my understanding that ParameterContainer::addParameter takes ownership of the passed Parameter (it uses the IPtr constructor that doesnt add to refcount, so it stays 1 after addParameter and it gets released in ParameterContainer::removeAllParams and the destructor). The official again example seems to be consistent with this.

Also I am not sure that hosts even interact with the parameter reference (instead they use the getParameterInfo/getParamNormalized/etc API which uses parameters IDs to refer to them)

Correct me if I'm wrong

[baconpaul]

Right so you are saying the code *and * the comment are wrong! Got it.

@defiantnerd - you have git attribution for that addRef. Thoughts?

The unique ptr changes all look great to me! It's just that addRef I want to have someone else eye up.

Thanks!