Split IPluginBase from IComponent

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.

docs/vst3.md

@@ -2,6 +2,8 @@
 
 TODO: Flesh this out further
 
+TODO: Link to `src/common/serialization/vst3/README.md`
+
 The VST3 SDK uses an architecture where every concrete object inherits from an
 interface, and every interface inherits from `FUnknown`. `FUnkonwn` offers a
 dynamic casting interface through `queryInterface()` and a reference counting