[REQ][ASPNET] Create .NET 8 (or 10) ASP.NET server template

Is your feature request related to a problem? Please describe.

The ASP.NET server generation is old and outdated. The available project templates and README are no longer up to date, and official Docker images for recent .NET versions do not exist.

Describe the solution you'd like

A new generator template for ASP.NET targeting .NET 8 should be created. If there are concerns about breaking changes, default to .NET 10. The solution should provide:

• Up-to-date project scaffolding for modern .NET (8 and/or 10)
• An updated README (whatever is auto-generated is fine)
• Official Docker images

This will help reduce confusion and manual workaround requirements for consumers who need/want modern .NET support.

Describe alternatives you've considered

• Using other generators/tools, such as swagger-gen
• Manually updating generated files

Additional context

I'd like to use .NET 8 as a baseline, but if breaking changes are an issue, we can start with .NET 10.

I'm willing to create a PR.

UPDATE:
Ah, determineTemplateVersion() provides an easy switch for how to handle .NET 8 (old or new template).
We also want to add 9.0 and 10.0 as valid values of aspnetCoreVersion.

I think I would create a 10.0 template to be the most modern and if .NET 9 works with it, great! If not, it can use the old one. .NET 8 and 9 go out of support in November, so we don't need to be overly concerned about those.

Start by locating determineTemplateVersion() and the handling of aspnetCoreVersion, then inspect the existing ASP.NET server template and its README and Docker configuration. Done means a modern .NET 8, 9, or 10 template is selected consistently, supported version values work, the README is current, and official Docker images are provided.