Add Ubuntu 26.04 (Resolute Raccoon) images

[lbussell]

Ubuntu 26.04 LTS "Resolute Raccoon" is scheduled to release on April 23, 2026.

Per our supported platforms policy, when new Ubuntu LTS versions are released, images are added for the latest .NET version and the latest LTS .NET version (if they differ). At the time of Ubuntu 26.04's release, .NET 10 will be both the latest released version and the latest LTS, so:

• Add resolute images for .NET 10
• Do nothing for .NET 8 or .NET 9
• Ship only resolute (for Ubuntu) for .NET 11 when it releases

.NET 11 preview images based on resolute are already available in the nightly repos.

[richlander]

Sounds good. Can we do same day release for resolute like we did for noble? I can do a blog post.

[lbussell]

Since Resolute images are opt-in for .NET 10, I think we can ship them early, on April Patch Tuesday (2026-04-14).

[richlander]

Related: dotnet/runtime#125535