Infer WinExe output type as appropriate

[dsplaisted]

If a project file specifies an OutputType of Exe, we should automatically change it to WinExe if any of the following are true:

• TargetPlatformIdentifier is windows (which will be the case if the TargetFramework is net5.0-windows
• UseWindowsForms or UseWPF is true (this will cover projects that target .NET Core 3.x and thus don't have the TargetPlatformIdentifier set to Windows

[Nirmal4G]

What If I want the console subsystem with the above cases? will there be an opt-out?

[wjk]

I am writing an otherwise-100% console-based app that shows WPF-based UI in one certain circumstance. Having WPF imply WinExe would break my project's intended use-case. If I can workaround this by moving all the WPF stuff into a DLL, that's fine by me.