Add code action support in BI extension

[kanushka]

Problem

Currently, when diagnostics or errors appear within the BI extension, users lack a mechanism to automatically resolve them. This creates friction in the development workflow, particularly within the expression editor, forms, and diagrams.

Proposed Solution

Integrate the existing Language Server Protocol (LSP) Code Action feature into the BI extension. This will enable:

• Auto-fixes: Allow users to resolve common diagnostic issues with a single click.
• Improved UX: Streamline error handling in the expression editor and form builders.
• Consistency: Leverage standard language server capabilities to maintain parity with other development tools.

Scope

• Expression Editor: Quick fixes for syntax and logic errors.
• Forms: Automated corrections for configuration mismatches.
• Diagrams: Resolve warnings and errors showed in diagrams.

[kanushka]

Tried building this on top of the current CodeAction APIs, but we're missing some diagnostic range info to get it working fully. Putting this on hold for now until the LS API fixes land

[kanushka]

We are introducing "Quick Fix" capabilities through both standard CodeActions and BI-Copilot (AI Agent). This requires the following updates:

1. LS API Enhancements

• getFlowModel: Update to include diagnostic ranges (start/end positions). This allows the extension to get CodeActions to specific code blocks and show the "Fix" button.
• getDesignModel: Integrate diagnostic data to ensure errors are visible and actionable within the component-diagram.

2. BI-Copilot Integration

• Contextual Fixes: Enable the extension to open BI-Copilot with a specific node range and diagnostic message pre-loaded.
• AI Remediation: The agent will use this context to automatically perform fixes for the user.

[kanushka]

Update ballerina-language-server API flowDesignService/getFlowModel to support source code range information for diagnostics.

ballerina-platform/ballerina-language-server#713