Install all .NET versions in pipeline to fix run tests task

Author: msbw2

build/template-Build-run-tests-sign.yml

@@ -7,6 +7,24 @@ steps:
 - script: echo $(MicrosoftIdentityModelVersion)
   displayName: 'display MicrosoftIdentityModelVersion'
 
+- task: UseDotNet@2
+  displayName: 'Use .Net Core SDK 2.x'
+  inputs:
+    version: 2.x
+    installationPath: $(Agent.ToolsDirectory)/dotnet
+
+- task: UseDotNet@2
+  displayName: 'Use .Net Core SDK 6.x'
+  inputs:
+    version: 6.x
+    installationPath: $(Agent.ToolsDirectory)/dotnet
+
+- task: UseDotNet@2
+  displayName: 'Use .Net Core SDK 8.x'
+  inputs:
+    version: 8.x
+    installationPath: $(Agent.ToolsDirectory)/dotnet
+
 - task: UseDotNet@2
   displayName: 'Use .Net Core SDK 9.x'
   inputs: