Use Gemini-1.5-pro-latest Stream Chat with history, Generate Git Commit message with Gemini, Add a Gemini Extension webview window, Chat mesage with Highlight Code

[JasonQWJ]

Description of the change

This pull request introduces a comprehensive set of enhancements to the Pipet Code Agent, focusing on user interface improvements, interaction refinements, and expanded functionality. Key changes include:

• Refined Chat Interface: The chat interface has been redesigned for better clarity and user experience. This includes visual improvements and adjustments to the layout for a more intuitive interaction.
• Enhanced Interaction: The interaction flow within the chat has been streamlined. This includes improvements to message handling, code highlighting, and overall responsiveness.
• Custom Commit Messages: Users now have the flexibility to provide custom commit messages when utilizing the agent's Git commit generation feature. This allows for more personalized and informative commit history.
• Updated Gemini Model: The underlying Gemini model has been updated to gemini-1.5-pro-latest to leverage the latest advancements and capabilities.
• API Updates: The codebase has been adapted to utilize the v1beta API and incorporates systemInstruction for improved control and interaction with the model.
• Bug Fixes and Optimizations: Several bug fixes and optimizations have been implemented to ensure a smooth and reliable user experience.

  Motivation

  These changes are driven by the goal of providing a more user-friendly, efficient, and feature-rich experience for Pipet Code Agent users. The refined interface and interaction aim to make the agent more intuitive and enjoyable to use. The addition of custom commit messages empowers users with greater control and flexibility over their Git workflow. Updating the Gemini model and API ensures the agent benefits from the latest advancements in AI technology. Bug fixes and optimizations contribute to a more stable and reliable user experience.

  Type of change

  Feature request

Checklist

• [x] I have performed a self-review of my code.
• [x] I have added detailed comments to my code where applicable.
• [x] I have verified that my change does not break existing code.
• [x] My PR is based on the latest changes of the main branch (if unsure, please run git pull --rebase upstream main).
• [x] I am familiar with the Google Style Guide for the language I have coded in.
• [x] I have read through the Contributing Guide and signed the Contributor License Agreement.

[MarkDaoust]

@joefernandez @shilpakancharla @markmcd - Codeowners says this should have gone to you, looks like we need to update it.