fix(entities-plugins): ai-proxy-advanced form

[Leopoldthecoder]

Summary

This is a temporary workaround for the issue that the ai-proxy-advanced plugin cannot be created if users don't provide config.embeddings or config.vectordb.

KM-675

[sumimakito]

Manually tested and the submission via the button worked as expected.

One more thing: Would we want to keep the model shown in View Configuration consistent with the final payload that will be submitted by us?

Configuration	Request payload

[Leopoldthecoder]

Ideally yes, we should keep them consistent. But it is not easy to do given the current implementation, as we are copying the payload so that it can be transformed. Will revisit if necessary.