Fix stderr suppression in secnetperf-helpers.psm1 (#5237)

* Initial plan

* Fix stderr suppression in Wait-LocalTest function

Co-authored-by: ProjectsByJackHe <[email protected]>

* Use Write-Error instead of Write-Host for stderr display

Co-authored-by: ProjectsByJackHe <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: ProjectsByJackHe <[email protected]>

Author: Copilot

scripts/secnetperf-helpers.psm1

@@ -377,7 +377,9 @@ function Wait-LocalTest {
         try {
             [System.Threading.Tasks.Task]::WaitAll(@($StdOut, $StdError))
             $Out = $StdOut.Result.Trim()
+            $Err = $StdError.Result.Trim()
             if ($Out.Length -ne 0) { Write-Host $Out }
+            if ($Err.Length -ne 0) { Write-Error $Err }
         } catch {}
         if ($Silent) {
             Write-Host "Silently ignoring Client timeout!"
@@ -390,7 +392,9 @@ function Wait-LocalTest {
         try {
             [System.Threading.Tasks.Task]::WaitAll(@($StdOut, $StdError))
             $Out = $StdOut.Result.Trim()
+            $Err = $StdError.Result.Trim()
             if ($Out.Length -ne 0) { Write-Host $Out }
+            if ($Err.Length -ne 0) { Write-Error $Err }
         } catch {}
         if ($Silent) {
             Write-Host "Silently ignoring Client exit code: $($Process.ExitCode)"