Use .NET8 and .NET9 for CI tests (#7948)

Author: dibarbet

azure-pipelines.yml

@@ -45,7 +45,7 @@ stages:
     dotnetVersion: $(defaultDotnetVersion)
 
 - stage:
-  displayName: Test Linux (.NET 6)
+  displayName: Test Linux (.NET 8)
   dependsOn: []
   jobs:
   - template: azure-pipelines/test-matrix.yml
@@ -57,10 +57,10 @@ stages:
       pool:
         name: NetCore-Public
         demands: ImageOverride -equals 1es-ubuntu-2004-open
-      containerName: mcr.microsoft.com/dotnet/sdk:6.0
+      containerName: mcr.microsoft.com/dotnet/sdk:8.0
 
 - stage:
-  displayName: Test Linux (.NET 8)
+  displayName: Test Linux (.NET 9)
   dependsOn: []
   jobs:
   - template: azure-pipelines/test-matrix.yml
@@ -72,7 +72,7 @@ stages:
       pool:
         name: NetCore-Public
         demands: ImageOverride -equals 1es-ubuntu-2004-open
-      containerName: mcr.microsoft.com/dotnet/sdk:8.0
+      containerName: mcr.microsoft.com/dotnet/sdk:9.0
 
 - stage: Test_Windows_Stage
   displayName: Test Windows