Fix using .NET Core assemblies for MSBuild tasks within VS

We had to revert the usage of .NET core assemblies in VS (#25417) because it ran into problems (https://devdiv.visualstudio.com/DevDiv/_workitems/edit/2968169).

The problem also reproduces when building Mac Catalyst from VS, so this doesn't only happen for remote iOS builds: https://devdiv.visualstudio.com/DevDiv/_workitems/edit/3013050 (using a Mac Catalyst project might be easier to test with, since there won't be any remoting).

We'll need to figure out and fix these problems.

Note: the usage of the .NET core assemblies is disabled in two places:
* https://github.com/dotnet/macios/pull/25662/changes
* e67eb98d3e680e7086e9b785bd76c03d22061a24 (#25417)