Clean up package metadata

[bricelam]

A few things I noticed while releasing:

• The copyright should be updated (at least the year)
• Packages should include a dependency on EFCore.Design

[lorcQc]

Good evening , I just changed the copyright year in the last commit.

[lorcQc]

When we add our package to a project, if we forget to add a reference to Microsoft.EntityFrameworkCore directly or by installing a package for a provider, our project no longer compiles (The source file we add requires DesignTimeServicesReferenceAttribute ).
When we see the error, you might think we need a reference to EFCore.Design, but that doesn't solve the problem...
This is what happened during the live demo made by ErikEJ last month.

Of course, we need EFCore.Design to use our package, but at least we get a clear message after typing a migration or scaffolding command if we don't reference it (and we are still able to compile the project).

I don't know if we can improve this.

[bricelam]

I think we should remove PrivateAssets="All" from the PackageReference to EFCore.Design.