Feat/embedding only support colang 2

[Pouyanpi]

• Add test for embeddings only and fallback_intent in Colang 2
• Fix a bug: fall back intent must be used when the embedding only branch does not return any intent.

[drazvan]

@Pouyanpi : I think there's a bug in both Colang 1 and 2 implementations. The threshold is meant to be for the top choice confidence. But if none is above that, and I don't have a fallback intent, then no examples are used either (because the search is performed only once with the threshold). Can you double-check? In the fallback with no intent, we should include the top 5 examples regardless of their similarity score.

[Pouyanpi]

In the fallback with no intent, we should include the top 5 examples regardless of their similarity score.

@drazvan, let me clarify my understanding of this:

Scenario: We are using embeddings exclusively with a search threshold and no fallback intent.

• If the search threshold filters out all results, leaving the result set empty, we ignore the threshold and return the top 5 results regardless of their similarity scores.
• However, if there are any results that meet the search threshold (even if fewer than 5), we keep only those results.