virtual declarations missing for `get_constrained_sizedtypes()` and `get_constrained_sizedtypes()` in `model_base`

Summary:

stanc outputs methods for returning a json-formatted string of the parameter metadata, like the following for the bernoulli model:

  inline std::string get_constrained_sizedtypes() const {
    return std::string("[{\"name\":\"theta\",\"type\":{\"name\":\"real\"},\"block\":\"parameters\"}]");
  }
  inline std::string get_unconstrained_sizedtypes() const {
    return std::string("[{\"name\":\"theta\",\"type\":{\"name\":\"real\"},\"block\":\"parameters\"}]");
  }

But these methods don't have corresponding virtual methods in src/model/model_base.hpp

Current Version:

v2.31.0

Start in src/model/model_base.hpp and compare its model interface with the methods stanc generates for constrained and unconstrained sized types. Confirm the generated output using the bernoulli example or another stanc-generated model; done means both methods have corresponding virtual declarations in model_base.hpp and the relevant compilation checks pass.