Multiple SDK versions available from `dotnet` command

[marcinjahn]

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

Normally, the dotnet command has access to all SDK versions installed in the system. You can list available versions with dotnet list-sdks. When multiple versions of .NET SDK are installed via asdf, each version has access to just the one version of SDK associated with it.

Describe the solution you'd like

It'd be awesome to have each version having access to its version number and all the previous ones as well. E.g., if I install dotnet 8 and dotnet 6 via asdf, I should get:

• SDK v6 and SDK v8 when I switch do version 8 via asdf
• SDK v6 only when I switch to version 6 via asdf