Enable signing of nuget.org packages and update to supported timestamp server (GH-23132)

.azure-pipelines/windows-release/stage-pack-msix.yml

@@ -120,10 +120,11 @@ jobs:
       artifactName: unsigned_msix
       downloadPath: $(Build.BinariesDirectory)
 
+  # MSIX must be signed and timestamped simultaneously
   - powershell: |
       $failed = $true
       foreach ($retry in 1..3) {
-          signtool sign /a /n "$(SigningCertificate)" /fd sha256 /t http://timestamp.verisign.com/scripts/timestamp.dll /d "$(SigningDescription)" (gi *.msix)
+          signtool sign /a /n "$(SigningCertificate)" /fd sha256 /tr http://timestamp.digicert.com/ /td sha256 /d "$(SigningDescription)" (gi *.msix)
           if ($?) {
               $failed = $false
               break

.azure-pipelines/windows-release/stage-pack-nuget.yml

@@ -4,7 +4,7 @@ jobs:
   condition: and(succeeded(), eq(variables['DoNuget'], 'true'))
 
   pool:
-    vmImage: windows-2019
+    name: 'Windows Release'
 
   workspace:
     clean: all
@@ -36,6 +36,14 @@ jobs:
       nuget pack "$(Build.BinariesDirectory)\layout\python.nuspec" -OutputDirectory $(Build.ArtifactStagingDirectory) -NoPackageAnalysis -NonInteractive
     displayName: 'Create nuget package'
 
+  - powershell: |
+      gci *.nupkg | %{
+        nuget sign "$_" -CertificateSubjectName "$(SigningCertificate)" -Timestamper http://timestamp.digicert.com/ -Overwrite
+      }
+    displayName: 'Sign nuget package'
+    workingDirectory: $(Build.ArtifactStagingDirectory)
+    condition: and(succeeded(), variables['SigningCertificate'])
+
   - task: PublishBuildArtifacts@1
     displayName: 'Publish Artifact: nuget'
     inputs:

.azure-pipelines/windows-release/stage-sign.yml

@@ -57,7 +57,7 @@ jobs:
       $files = (gi ${{ parameters.Include }} -Exclude ${{ parameters.Exclude }})
       $failed = $true
       foreach ($retry in 1..10) {
-          signtool timestamp /t http://timestamp.verisign.com/scripts/timestamp.dll $files
+          signtool timestamp /tr http://timestamp.digicert.com/ /td sha256 $files
           if ($?) {
               $failed = $false
               break