Instead of serializing the actual `YaMessage`, for the reasons mentioned
in the comments. This was needed to stop iZotope VocalSynth 2 in Ardour
from segfaulting when editing parameters, because that plugin is
apparently being very naughty.
This is quite a huge refactor, but note everything is consistent (and
we're going to need one or two more of these `Vst3*Proxy` objects).
Right now nothing extends `IHostApplication`, but this way it will be
trivial to add support for more host context interfaces.
We can now use implement all VST3 plugin interfaces through this class,
check whether the object from the plugin also supports these classes,
and then conditionally allow casting to the supported classes. This
should give us a one-to-one proxy of the original object.
We're also going to need this for `IEditController`. Separating all of
these classes will also keep everything much more maintainable with all
of these associated structs.
Directly serializing and deserializing into objects was and more
boilerplate heavy (since we now need two implementations even though we
only use one), and also much less flexible because we can't wrap
payloads in structs or provide optional values that way.
Transferring some argument pack is much easier than trying to
deserialize into an existing object when you also have to transfer more
information than just that object.
And add separate implementations for the native plugin and the Wine
plugin host. This way we can easily allow the native host to do
callbacks without having to manage a load of lambdas.
Robbert van der Helm