.NET Core 2.1.16

Pin Cryptography.Cng (dotnet#2894)

Revert "Remove ref project from Microsoft.AspNetCore.Testing (dotnet#…

…2817)" (dotnet#2882)

This reverts commit b624d6b.

Merge in 'release/3.1' changes

Merge in 'release/3.0' changes

.NET Core 3.1.0

Update branding to 2.1.15 (dotnet#2692)

.NET Core 3.1 preview3

Fixup sha and pin NETStandard.Library.Ref (dotnet#2582)

.NET Core 3.1.0 Preview 2