Retry NuGet signature validation

[dougbu]

• see NuGet restore fails with The repository primary signature validity period has expired #13070
• more details: https://learn.microsoft.com/en-us/nuget/reference/errors-and-warnings/nu3028#retry-untrusted-root-failures

To double check:

• The right tests are in and and the right validation has happened. Guidance: https://github.com/dotnet/arcade/tree/main/Documentation/Validation

[dougbu]

/ping reviewers

[dougbu]

@markwilkie what are your thoughts on backporting this fix to release/6.0 and release/7.0❔ Our Helix Machines infrastructure hit the problem and uses a 6.0 SDK.

[garath]

what are your thoughts on backporting this fix to release/6.0 and release/7.0

@dougbu I say go ahead and open the PRs. The right people will be involved in the review there.

[dougbu]

/backport to release/6.0

[github-actions]

Started backporting to release/6.0: https://github.com/dotnet/arcade/actions/runs/5137651299

[dougbu]

/backport to release/7.0

[github-actions]

Started backporting to release/7.0: https://github.com/dotnet/arcade/actions/runs/5137656450