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

Merge pull request dotnet#2469 from aspnet/darc-release/3.1-preview1-…

…6d67e924-2a34-48e3-b2bc-d7a0905dd016

[release/3.1-preview1] Update dependencies from dotnet/core-setup

Merge branch 'release/2.1' => 'release/2.2' (dotnet#2383)

Update branding to 2.1.14

- aspnet/AspNetCore-Internal#3153
- give daily build output more-reasonable versions