Improve plugin installation by automating at least the version numbers to be aligned with the NuGet version

[einari]

Today we are maintaining NuGet package versions in the .csproj file and then manually inside the PulumiOperations.cs file. It would ideally figure out which plugins based on the NuGet references and then install these with correct version and all. Secondary, at least should it use the assembly version from the equivalant NuGet package.