Let dotnet scaffold target net8 9 10 11

[haileymck]

• Allow for dotnet scaffold to target net 8, 9, 10, 11 projects
• adds unit tests for targeting each net 8, 9, 10, 11 projects
• adds specific package versions for each net 8, 9, 10, 11 projects in Versions.props
  Note this may change how the automated package update PRs are configured
• Allows for finding the correct CodeModificationConfigFile for the version of .NET of the project. Note that these different files live in their respective .net folder
• Allows for finding the correct .tt template file for the version of .NET of the project. The files are used to generate code in the users' project. Note that these different files live in their respective .net folder
• if invalid project file, defaults to the templates for net 11 projects.
• fixes UseExistingApplication misspelling

fixes #3529
fixes #3530
fixes #3537