Add Support for new OpenAI model GPT-4o-mini + improve prompts

[mondaychen]

Description

This PR adds support for gpt-4o-mini model.
After testing, I noticed that because this is a smaller model, its ability to follow instructions and examples is weaker than recommended models. For example, it often responses with label: "Search Amazon" instead of label: 3
It's probably because it confuses the name "label" with html label.
I've also included a prompting improvement in this PR, which renames label to uid so it's easier for small models to understand the value in needs to be one of uids provided in context, not html label.

Type of Change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Documentation update
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Build-related changes
• Other (please describe):

How Has This Been Tested?

I have tested the change with gpt-4o-mini as well as non-vision model (gpt-4_

Screenshots (if applicable)