Simplify model submission checking to a dedicated PRECHECK state

[donaldknoller]

When a miner model is first submitted, there are multitude of steps done before it is properly added to the evaluation queue.
Some of these steps include (but are not limited to)

1. Check if huggingface repo is public
2. Check model repo size
3. Check hashes of safetensors

These steps are likely better executed in a dedicated check, and will allow for additional steps in the future to be added.
Thus, the implementation of a PRECHECK state will help better execute the above.