Improve build speed with incremental builds

Description

Improved the build speed in projects by copying shell module files when they change or are missing.

Formerly, these files were copied and overwritten on every build with the CopyZipFiles.target being executed. In projects where zip modules files are included in the repository (such as modules/_protected/CMS.zip or Shell.zip), those files are no longer overwritten on each build.

Optimizely projects on .NET core should exclude all modules from the source repository because those files are automatically recreated when missing during the dotnet build.