[TrimmableTypeMap] Revisit delayed registerNatives mechanism for Application and Instrumentation subclasses

Application and Instrumentation java classes are loaded before the .NET runtime is initialized. This means we can't use `static { ... }` to register native methods and we implemented 2 separate ways of working around this:
- `ApplicationRegistration.java` - generated code which we can call manually from JNIEnvInit and where we can register native methods for all the types that need it (very few usually)
- lazy call to `registerNatives` from the generated java constructors of the Application and Instrumentation subclasses (and also from static methods)

We should settle on just one approach and simplify the generator code. I suggest removing the `ApplicationRegistration` class and only use the lazy registration just before the first `native` method is called.