Support for Gemini tool calling (plus general fixes)

[marklysze]

Why are these changes needed?

The Gemini class doesn't currently support tool calling.

This PR adds tool calling.

Additional updates:

• Removal of role alternation, this no longer appears necessary
• Image input corrected for non-Vertex AI
• Costs updated

NOTE: This hasn't been tested with Vertex AI authentication, if someone can test it that would be good. Please try the client test files in my repo.

Related issue number

Noted in Discord issue

Checks

• I've included any doc changes needed for https://ag2ai.github.io/autogen/. See https://ag2ai.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[qingyun-wu]

@marklysze there are conflicts. Could you fix the conflicts in this PR or draft a new PR? Thank you!

[luxzoli]

@marklysze I have found a few minor issues when testing it with VertexAI using some of my own tests. I would still have to go through your tests. Should I prepare a PR to your branch for the suggested (minor) changes to support VertexAI as well?

[marklysze]

@marklysze I have found a few minor issues when testing it with VertexAI using some of my own tests. I would still have to go through your tests. Should I prepare a PR to your branch for the suggested (minor) changes to support VertexAI as well?

Thanks for that @luxzoli! It would be great if you could work on this branch.

Let me update the branch in line with main now.

[marklysze]

@luxzoli, would you be on Discord as well? If so, can you let me know your Discord ID? If you want to message me on there, my Discord ID is msze_

[marklysze]

Thanks @luxzoli, branch is updated, let me know how you go :)

[qingyun-wu]

@marklysze could you fix the conflicts? Thank you!

[marklysze]

@marklysze I have found a few minor issues when testing it with VertexAI using some of my own tests. I would still have to go through your tests. Should I prepare a PR to your branch for the suggested (minor) changes to support VertexAI as well?

Hi @luxzoli, I'll merge this one as we're due for a release, if there are VertexAI changes or other fixes, can you please create a new PR?

[luxzoli]

@marklysze I have found a few minor issues when testing it with VertexAI using some of my own tests. I would still have to go through your tests. Should I prepare a PR to your branch for the suggested (minor) changes to support VertexAI as well?

Hi @luxzoli, I'll merge this one as we're due for a release, if there are VertexAI changes or other fixes, can you please create a new PR?

Sure! Nevertheless, yesterday I have tested the function calling again with VertexAI, and my original fix is not needed anymore 🙂
For other things I will create a new PR then