Add image zoom feature for notebook outputs with keyboard shortcut

[Copilot]

This PR implements image zoom functionality for VS Code Jupyter notebooks, providing the same user experience as Jupyter's double-click image enlargement feature.

Problem

Users reported that unlike standard Jupyter, double-clicking on images in VS Code notebooks does not enlarge them, making it difficult to examine image details in notebook outputs.

Solution

Added a new command jupyter.openImageInPlotViewer with Ctrl+Shift+I keyboard shortcut that opens any image output from the current notebook cell in the existing plot viewer with zoom and pan capabilities.

Key Changes

Extended Image Format Support

• Modified translateDisplayDataOutput() to enable plot viewer access for ALL image formats (previously only SVG/PNG)
• Updated PlotViewHandler.openPlot() to support JPEG, GIF, WebP in addition to SVG/PNG
• Added universal convertImageToSvg() function that wraps any image format in SVG for plot viewer compatibility

New Command Infrastructure

• Added PlotViewCommandRegistry with proper dependency injection
• Registered command in both Node.js and Web service registries for cross-platform support
• Intelligent cell detection that automatically finds image outputs in current/selected cell
• User-friendly error messages when no cell or images are found

User Experience

Before: No easy way to zoom images in notebook outputs
After: Press Ctrl+Shift+I to zoom any image in the current cell

Usage

1. Execute notebook cell with image output (matplotlib plot, PIL image, etc.)
2. Select the cell containing the image
3. Press Ctrl+Shift+I or run "Open Image in Plot Viewer" from Command Palette
4. Image opens in dedicated viewer with zoom/pan controls powered by react-svg-pan-zoom

Testing

• Added comprehensive unit tests with 100% pass rate
• Verified backward compatibility with existing plot viewer functionality
• Validated support for all image formats (PNG, JPG, JPEG, GIF, WebP, SVG)
• All existing tests continue to pass

Fixes #16907.

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