feat: implement SQL Notebook (.sqlnb) support for SQLTools

[hnhonnguyen]

Add SQL Notebook (.sqlnb) Support

Description

This PR implements a new SQL Notebook feature for SQLTools, allowing users to create, edit, and execute SQL queries in notebook format with the .sqlnb extension. This feature enhances the user experience by providing an interactive environment for SQL development and data exploration.

Key Features

• SQL Notebook format (.sqlnb) for running SQL queries in notebook cells
• Support for connecting each cell to different database connections
• Cell-level metadata for connection management
• Interactive result display with HTML tables
• Export options for query results (CSV, JSON)
• Result limiting functionality for large datasets
• Connection status indicators in cell status bar
• Notebook serializer for saving and loading .sqlnb files

Technical Implementation

• Added notebook controller and serializer for managing SQL notebooks
• Integrated with existing SQLTools connection management system
• Implemented cell execution with query results displayed as HTML tables
• Added UI elements and commands for notebook interaction
• Added necessary icons and updated package.json for new notebook type

Testing

• Tested with various database connections
• Verified cell execution and result display
• Confirmed notebook serialization/deserialization
• Tested export functionality for query results

Notes

The notebook implementation follows VS Code's notebook API and integrates seamlessly with SQLTools' existing connection management, providing a powerful and user-friendly interface for SQL development.

---

• Your code builds clean without any errors or warnings
• You have made the needed changes to the docs
• You have written a description of what is the purpose of this pull request above