[workload] use **FromWorkload** for targeting/runtime pack versions

[jonathanpeppers]

Description of Change

Context: dotnet/sdk#19596

If we use the version number string of **FromWorkload**, then our
runtime packages don't need to be resolved from a NuGet feed. They can
be resolved from the dotnet/packs directory.

This completely eliminates the need for a NuGet.config file for
projects when you have the maui workload installed.

One caveat for dotnet/maui is we have a $(MicrosoftMauiSdkVersion).
We'll need to use **FromWorkload** in some places, and the actual
number when declaring @(PackageReference).

PR Checklist

• Targets the correct branch
• Tests are passing (or failures are unrelated)
• Targets a single property for a single control (or intertwined few properties)
• Adds the property to the appropriate interface
• Avoids any changes not essential to the handler property
• Adds the mapping to the PropertyMapper in the handler
• Adds the mapping method to the Android, iOS, and Standard aspects of the handler
• Implements the actual property updates (usually in extension methods in the Platform section of Core)
• Tags ported renderer methods with [PortHandler]
• Adds an example of the property to the sample project (MainPage)
• Adds the property to the stub class
• Implements basic property tests in DeviceTests

Does this PR touch anything that might affect accessibility?

No

[jonathanpeppers]

Whoops, this needs at least .NET 6.0.100-rc.1.21412.2, and dotnet/maui has 6.0.100-rc.1.21408.2.

I'll come back to this later.

[jonathanpeppers]

When this lands, I can come back to this: #2103

[mattleibow]

What is the testing process for this? If I do a dotnet new, then it will restore from nuget.org.

[jonathanpeppers]

It looks like things have changed a little since I last looked at your CI:

maui/eng/pipelines/handlers.yml

Lines 220 to 223 in e84735d

	- pwsh: ./build.ps1 --target=dotnet-local-workloads --configuration="${{ BuildConfiguration }}" --verbosity=diagnostic
	displayName: 'Install .NET (Local Workloads)'
	- pwsh: ./build.ps1 --target=dotnet-samples --configuration="${{ BuildConfiguration }}" --verbosity=diagnostic
	displayName: 'Build .NET 6 Samples'

If this is still running this, it should be testing it:

$ dotnet build src/DotNet/DotNet.csproj -p:InstallWorkloadPacks=false
$ ./bin/dotnet/dotnet build src/DotNet/DotNet.csproj -t:Install
$ ./bin/dotnet/dotnet build Microsoft.Maui.Samples-net6.slnf -p:UseWorkload=true

At some point, should CI do dotnet new maui with no NuGet.config, and makes sure it can build?