Add a .NET iOS & Mac Catalyst sample and .NET "Core" sample support

[mattleibow]

Description of Change

Adding a new iOS and Mac Catalyst sample.

Also, there is now support for building samples with .NET [Core]. You can opt into this by adding a solution (or solution filter) that has a -net suffix:

Solution Name	.NET / MSBuild	Platform
Sample.sln[f]	MSBuild	All
Sample.Windows.sln[f]	MSBuild	Windows
Sample.Mac.sln[f]	MSBuild	macOS
Sample.Linux.sln[f]	MSBuild	Linux
Sample.Windows-net.sln[f]	.NET	Windows
Sample.Mac-net.sln[f]	.NET	macOS
Sample.Linux-net.sln[f]	.NET	Linux

NOTE: Sample-net.sln[f] is not supported yet as the logic is really rudimentary. It assumes the first component is the solution name and is located using a basic wildcard.