Sync eng/common directory with azure-sdk-tools for PR 7877 (#28928)

Sync eng/common directory with azure-sdk-tools for PR
Azure/azure-sdk-tools#7877 See [eng/common
workflow](https://github.com/Azure/azure-sdk-tools/blob/main/eng/common/README.md#workflow)

---------

Co-authored-by: Scott Beddall (from Dev Box) <scbedd@microsoft.com>

eng/common/testproxy/test-proxy-tool-shutdown.yml

@@ -0,0 +1,10 @@
+steps:
+  - pwsh: |
+      Stop-Process -Id $(PROXY_PID)
+    displayName: 'Shut down the testproxy - windows'
+    condition: and(succeeded(), eq(variables['Agent.OS'],'Windows_NT'))
+
+  - bash: |
+      kill -9 $(PROXY_PID)
+    displayName: "Shut down the testproxy - linux/mac"
+    condition: and(succeeded(), ne(variables['Agent.OS'],'Windows_NT'))

eng/common/testproxy/test-proxy-tool.yml

@@ -1,3 +1,4 @@
+# This template sets variable PROXY_PID to be used for shutdown later.
 parameters:
   rootFolder: '$(Build.SourcesDirectory)'
   runProxy: true
@@ -42,15 +43,20 @@ steps:
       condition: and(succeeded(), ${{ parameters.condition }})
 
     - pwsh: |
-        Start-Process $(Build.BinariesDirectory)/test-proxy/test-proxy.exe `
+        $Process = Start-Process $(Build.BinariesDirectory)/test-proxy/test-proxy.exe `
           -ArgumentList "start --storage-location ${{ parameters.rootFolder }} -U" `
           -NoNewWindow -PassThru -RedirectStandardOutput ${{ parameters.rootFolder }}/test-proxy.log
+
+        Write-Host "##vso[task.setvariable variable=PROXY_PID]$($Process.Id)"
       displayName: 'Run the testproxy - windows'
       condition: and(succeeded(), eq(variables['Agent.OS'],'Windows_NT'), ${{ parameters.condition }})
 
     # nohup does NOT continue beyond the current session if you use it within powershell
     - bash: |
         nohup $(Build.BinariesDirectory)/test-proxy/test-proxy &>$(Build.SourcesDirectory)/test-proxy.log &
+        
+        echo $! > $(Build.SourcesDirectory)/test-proxy.pid
+        echo "##vso[task.setvariable variable=PROXY_PID]$(cat $(Build.SourcesDirectory)/test-proxy.pid)"
       displayName: "Run the testproxy - linux/mac"
       condition: and(succeeded(), ne(variables['Agent.OS'],'Windows_NT'), ${{ parameters.condition }})
       workingDirectory: "${{ parameters.rootFolder }}"