[net7] include net6 templates

[Redth]

Description of Change

Since you can still build a net6.0-* MAUI app with the net7 SDK, we also want to ship the net6 template packs as part of the workload.

This adds the previous dotnet sdk template pack to the manifest.

Support

• Maui
• Android
  • Debug
  • Release
    Linker produces colliding MVID for two different inputs linker#2203
    Deterministic MVIDs is needed for assemblies referencing System.Private.CoreLib across different architectures runtime#67660
• Windows
• iOS/MacCat: Unable to build net6.0-ios in the .NET 7 SDK xamarin/xamarin-macios#15344
• Tizen: Unable to build a net6.0-tizen TFM on .NET 7 Samsung/Tizen.NET#182

[jonathanpeppers]

If you dotnet new maui, how does it decide which template to use?

[Redth]

If you dotnet new maui, how does it decide which template to use?

There's the new parameter for the sdk version, I think you can specify that in the CLI if you want to override the default which I believe is based on the dotnet sdk in the context you are running the command from.

[jonathanpeppers]

Should we test the new switch here:

maui/eng/cake/dotnet.cake

Lines 145 to 147 in a1a9a44

	foreach (var template in templates)
	{
	foreach (var forceDotNetBuild in new [] { true, false })

Basically test all the templates twice, once for 6 and once for 7.

[mattleibow]

Yeah, we can duplicate the stage with different parameters.

[mattleibow]

This PR with make it possible to run things for net6 and net7: #8237

I finally got the quotes to work, so once that is merged, I'll update this PR.

[rmarinho]

Executing: "bin/dotnet/dotnet.exe" new maui -o "D:/a/_work/_temp/templatesTest/maui_DotNet_net6.0" --framework net6.0
Error: Invalid option(s):
--framework
   '--framework' is not a valid option
net6.0
   'net6.0' is not a valid option

For more information, run:
   dotnet new maui -h

[mattleibow]

According to physics, that should be there for net7. According to CI it is not.

[mattleibow]

For another PR later:
https://github.com/dotnet/templating/blob/main/docs/Reference-for-template.json.md#multichoice-symbols-specifics

We can do amazing things with the actual target platforms and make the csproj beautiful-er

[mattleibow]

This needs to be replaced with the shipping version of MAUI SR2