[devops] Clean up temporary files on Windows before running remote tests. (#22221)

This is an attempt to fix a random connection issue:

>  Integrity check failed between source and target content. Source path: D:\AzDO\_work\16\s\xamarin-macios\tests\dotnet\Windows\bin\dotnet\packs\Microsoft.iOS.Windows.Sdk.net9.0_18.2\18.2.9451-ci.dev-rolf-xml-docs-1\tools\msbuild\iOS\Broker.zip, Target path: /Users/builder/Library/Caches/Xamarin/XMA/Agents/Broker/3.0.0.13

Ref: https://teams.microsoft.com/l/message/19:[email protected]/1740052447890?tenantId=72f988bf-86f1-41af-91ab-2d7cd011db47&groupId=0056f60b-301f-43ac-bbcf-f356d3c42c92&parentMessageId=1740052447890&teamName=VS%20Client%20Experiences&channelName=MaciOS%20%F0%9F%8D%8E&createdTime=1740052447890

Author: rolfbjarne

tools/devops/automation/templates/windows/build.yml

@@ -153,6 +153,19 @@ steps:
     }
   displayName: "Verify ssh connection"
 
+- pwsh: |
+    $remoteTmpPath = "${Env:LOCALAPPDATA}\Temp\Xamarin\XMA\Remote"
+    Write-Host "Remote tmp path: $remoteTmpPath"
+    # let's see what's there
+    if (Test-Path -Path $remoteTmpPath) {
+      Get-ChildItem -Path $remoteTmpPath
+      Get-ChildItem -Path $remoteTmpPath | Format-Table | Out-String | Write-Host
+      Remove-Item -Recurse -Force $remoteTmpPath
+    } else {
+      Write-Host "Remote tmp path doesn't exist!"
+    }
+  displayName: "Cleanup temporary files"
+
 # This task fixes errors such as these:
 #     error MSB4242: SDK Resolver Failure: "The SDK resolver "NuGetSdkResolver" failed while attempting to resolve the SDK "Microsoft.Build.NoTargets/3.3.0".
 #                    Exception: "NuGet.Packaging.Core.PackagingException: Unable to find fallback package folder 'D:\Program Files (x86)\Microsoft Visual Studio\Shared\NuGetPackages'.