rtk-query-codegen-openapi - allow to include all defined models in code generation

[llRandom]

Currently model is not generated if it's not used by generated endpoints even if model is defined in openapi spec. In some cases it's very helpful to allow including such models instead of copy-pasting them from the backend. As a workaround I can create dummy endpoints just to include models but it would be more convenient to opt-in extra models generation