mdlsub: types provider util for transformers

This release adds a small helper for mdlsub transformers.
Instead of implementing the GetInput and GetModel functions, one can embed the TypesProvider.

before

type TestTransformer struct{}

func (t TestTransformer) GetInput() any {
	return &TestInput{}
}

func (t TestTransformer) GetModel() any {
	return &TestModel{}
}

after

type TestTransformer struct {
	mdlsub.TypesProvider[TestInput, TestModel]
}