[Bug] Lists of values in "combo" primitive nodes can not change

## Behavior:
The dropdown list of primitive nodes with output type "COMBO" is fixed once created. For example, when using a primitive as the "ckpt_name" input to a checkpoint loader or a "lora_name" input to a lora loader, the list of models in the dropdown does not reflect changes to the filesystem, even after reloading the web ui and restarting the server.

I believe that this is happening because the web ui saves and loads the full list of possible values into json as the "type" field, and does not attempt to update this list when loading. If possible, I think it would be best to exclude the list of possible values from the json files entirely, as including them may lead to users leaking their full list of models online.

## Steps to reproduce:
1. Create a "Checkpoint Loader (Simple)".
2. Create another "Checkpoint Loader (Simple)", covert "ckpt_name" to an input, and connect a primitive node.
3. Modify the set of models in the filesystem.
4. Reload the web ui and/or restart the server.

The dropdown of the checkpoint loader will reflect changes to the filesystem, while the dropdown of the primitive node will not.