MapStaticAssets API cross-linking

[guardrex]

Addresses #32810

@Rick-Anderson @tdykstra @wadepickett ... Also knocking out old Duende links. In their docs system, they kill off old documentation and rotate links without redirects, so v5 links are no good and 404 💀. The best we can do is just link their top-level docs domain to harden our docs against future breaks, which is what I'm doing here repo-wide.

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Internal previews

📄 File	🔗 Preview link
aspnetcore/blazor/fundamentals/static-files.md	aspnetcore/blazor/fundamentals/static-files
aspnetcore/blazor/security/webassembly/hosted-with-identity-server.md	aspnetcore/blazor/security/webassembly/hosted-with-identity-server
aspnetcore/blazor/tutorials/movie-database-app/part-1.md	aspnetcore/blazor/tutorials/movie-database-app/part-1
aspnetcore/migration/50-to-60.md	aspnetcore/migration/50-to-60
aspnetcore/release-notes/aspnetcore-6.0.md	aspnetcore/release-notes/aspnetcore-6.0
aspnetcore/security/identity-management-solutions.md	aspnetcore/security/identity-management-solutions