feat: handle inherited methods in modal classes

[hholb]

While getting the fairchem models up and running in a modal app, I wanted to do something like this:

import modal

app = modal.App()

app.image = ...

# no decorator here so we don't publish a _BaseModel entrypoint
class _BaseModel():

     @modal.enter()
     def load_model(self):
          # common logic to load model checkpoints
           ...

     @modal.method()
     def run_inference(self):
         # common logic for inference
          ...


@app.cls(...)
class MyModel(_BaseModel):
    # modal picks up the load_model and run_inference methods from the base class
     ...


@app.cls(...)
class MyOtherModel(_BaseModel):
      ...

Modal accepts this kind of setup and handles associating the methods with the subclasses, but our current parsing for modal functions does not recognize the run_inference method as a member of the subclasses.

The backend should recognize two modal classes here, MyModel and MyOtherModel each with a run_inference method as the entrypoint. Currently, the backend recognizes the two model classes, but does not find the run_inference method and returns an empty list of modal functions for each model.