EF 6.6.0-preview1 released

You can download it from https://www.nuget.org/packages/EntityFramework/6.6.0-preview1-final

This is mostly a test run for our new release pipeline, but it also contains the fixes for https://github.com/dotnet/ef6/issues/2325 and https://github.com/dotnet/ef6/issues/2322

Please try it out and report any regressions.