Msbuild builder

[pepone]

This PR moves zeroc.icebuilder.msbuild builder into tools/Ice.Slice.Tools package.

Updates the C# build to use tasks from tools/Ice.Slice.Tools and avoid the dependency on zeroc.icebuilder.msbuild package.

Upgrades zeroc.ice.net NuGet package to include the builder. Later we will upgrade the demos to not require a separate builder package and just use zeroc.ice.net.

Next I will update Windows C++. NuGet package to do the same.

Opening as a Draft to get some feedback about the layout and general approach for doing this.

[bernardnormier]

What is the advantage of having a single tool that can handle both C++ (with slice2cpp) and C# (with slice2cs).

As I understand it, we'll ship this tool in the C++ NuGet and the C# NuGet - in the C++ NuGet together with slice2cpp (for multiple platforms) and in the C# NuGet together with slice2cs (for multiple platforms).

Is this because there is a lot of code in common? Because it's nicer to have a single tool (Ice.Slice.Tools), just like we have a single IceRpc.Slice.Tools?

[pepone]

What is the advantage of having a single tool that can handle both C++ (with slice2cpp) and C# (with slice2cs).

For the initial import, I’m keeping the zeroc.icebuilder.msbuild structure as is. I will improve this before making the PR ready for review/merge.

There’s no need to support both C++ and C# with the same tool—each package (zeroc.ice.net and zeroc.ice.v143) should include only what it needs.

For example, we could improve this by having:

• Ice.Slice.Tools.CSharp: The C# builder, support files, and project files
• Ice.Slice.Tools.Cpp: The C++ builder, support files, and project files
• Ice.Slice.Tools: Shared classes that both projects can include

The only packages users would need are zeroc.ice.net and zeroc.ice.v143.