Fix VertexAI bugs and add function calling

[Lash-L]

Description

Opening this in place of #3711 as it fixes all of the relevant problems instead of just one.

Seems like a bug was introduced when the embeddings were merged into the llm.
b14b8c4#diff-f6056e365b00006d0872276e5078b8e10b940dfeca7f0aa106b1c842e5aa5a14

The embedding class's base url didn't have a slash at the end, while the llm one did. Neither one was 'wrong', but they were different, so when it was merged, it ended up having a // in the url.

Removing the / before the embedding url fixes this problem.

As well, a bug was introduced in 3b25f78 that broke sending messages as it took the options out of the needed subsection.

Gemini via AI studio and VertexAI are very very similar. So I extracted out the logic that could be copied from the vertexai send and I now call it in VertexAI. This should help prevent any future issues and allow vertexAI's gemini deployment to piggyback on gemini's.

fixes #4166
fixes #3907
fixes #3595
fixes #3303

Checklist

• [] The relevant docs, if any, have been updated or created
• [] The relevant tests, if any, have been updated or created

Screenshots

[ For visual changes, include screenshots. ]

Testing instructions

[ For new or modified features, provide step-by-step testing instructions to validate the intended behavior of the change, including any relevant tests to run. ]

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[sestinj]

Can you add a test in llm.test.ts for the Vertex class? Shouldn't take much, just about 5 lines of code

[Lash-L]

Can you add a test in llm.test.ts for the Vertex class? Shouldn't take much, just about 5 lines of code

Hi are you looking for a TestLLM call? Or something else?

[Lash-L]

Hey @sestinj - sorry for the ping - just trying to figure out what kind of tests you would like to see.

[Lash-L]

@sestinj - I am looking at llm.test.ts and to add the LLMTest you need a active gcp account. And then it gets a bit tricky.

The vertex Ai extension auths via gcloud which is a cli object on your machine. You can't just set a API_KEY like you can for all of the other ones, it would be more complicated. You'd likely have to create a service account and store the credentials in a github secret. Is that what you are looking for when you ask for tests?