Replace bitmap-backed Visual Studio icons with ImageMonikers

[Copilot]

Summary

• replace the remaining bitmap-backed command icons in src/VisualStudio/ProjectPackage/Menus.vsct with image catalog monikers
• switch the VS 2022 X# project node, X# file node mappings, and shared reference container node to moniker-based hierarchy icons
• stop relying on the custom X# bitmap strip for these DEV17 command and hierarchy icon paths

Validation

• git --no-pager diff --check
• XML parse of /home/runner/work/XSharpPublic/XSharpPublic/src/VisualStudio/ProjectPackage/Menus.vsct
• dotnet build src/VSIntegration2022.sln -c Debug -v minimal (fails in this Linux sandbox because the repo's VS integration projects require Visual Studio/VSSDK targets, XSharp build props, and .NET Framework targeting packs)

[Copilot]

Pull request overview

This pull request modernizes the Visual Studio integration icons by moving remaining command and hierarchy visuals away from a custom bitmap strip and onto Visual Studio’s Image Catalog monikers (especially for VS 2022 / DEV17). This reduces reliance on bitmap-backed resources and aligns the extension UI with standard VS icon theming.

Changes:

• Updated Menus.vsct commands to use ImageCatalogGuid moniker icons (and removed the custom bitmap strip registration).
• Switched VS 2022 (DEV17) hierarchy icons for the X# project node and reference container to moniker-based icons.
• Consolidated X# file-extension-to-moniker mappings for better maintainability.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
src/VisualStudio/ProjectPackage/Nodes/XSharpProjectNode.cs	Uses icon monikers for the project node under DEV17 and gates bitmap image list loading/usage to non-DEV17.
src/VisualStudio/ProjectPackage/Nodes/XSharpFileNode.cs	Refactors and expands extension→moniker mappings; simplifies DEV17 moniker support logic.
src/VisualStudio/ProjectPackage/Menus.vsct	Replaces bitmap-backed command icons with Image Catalog monikers and removes the bitmap strip symbol/registration.
src/VisualStudio/ProjectBase/ReferenceContainerNode.cs	Enables moniker icons for the reference container under DEV17 and avoids bitmap-handle lookup in that configuration.

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