Simplify and fix ProcessWrapper.KillProcessTree

[Copilot]

KillProcessTreeInternal calls Process.Kill() without the entireProcessTree parameter, missing the native process-tree kill available since .NET Core 3.0. On NETFRAMEWORK, the method manually walks child processes via WMI — that path is unchanged.

• On non-NETFRAMEWORK targets, call process.Kill(entireProcessTree: true) directly in KillProcessTree, eliminating the need for KillProcessTreeInternal
• Moved KillProcessTreeInternal behind #if NETFRAMEWORK since it is only needed for the WMI-based recursive child process kill
• Ensured all Process instances are properly disposed via using
• Swallow all exceptions around the kill call so the helper remains best-effort and doesn't cause test flakiness, matching the original behavior
• Disposed WMI objects (ManagementObjectSearcher, ManagementObjectCollection, ManagementObject) in the NETFRAMEWORK path to prevent handle leaks

[adamsitnik]

@copilot I believe there is still place for improvement:

• we need to ensure every Process instance gets disposed
• we can simplify the non-framework impl

Following code is pseudocode, please take as inspiration, make sure you can build the product before pushing any changes.

        public static void KillProcessTree(int processId)
        {
            using Process? process = null;

            try
            {
                process = Process.GetProcessById(processId);
            }
            catch (ArgumentException)
            {
                // Process might have already exited.
                return;
            }

            if (!process.HasExited)
            {
#if NETFRAMEWORK
                KillProcessTreeInternal(process.ID);
#else
                process.Kill(entireProcessTree: true);
#endif
            }
        }

#if NETFRAMEWORK
        private static void KillProcessTreeInternal(int pid)
        {
            ManagementObjectSearcher searcher = new ManagementObjectSearcher("Select * From Win32_Process Where ParentProcessID=" + pid);
            ManagementObjectCollection moc = searcher.Get();
            foreach (ManagementObject mo in moc)
            {
                KillProcessTreeInternal(Convert.ToInt32(mo["ProcessID"]));
            }

            try
            {
                using Process proc = Process.GetProcessById(pid);
                proc.Kill();
            }
            catch (ArgumentException)
            {
                // vramak: Process might have already exited.
            }
        }
#endif

[Copilot]

@copilot I believe there is still place for improvement:

• we need to ensure every Process instance gets disposed
• we can simplify the non-framework impl
  ...

Applied both improvements in ddb2308:

• All Process instances are now disposed (using (process) in KillProcessTree, using (Process proc = ...) in KillProcessTreeInternal)
• Simplified the non-framework path: process.Kill(entireProcessTree: true) is called directly in KillProcessTree, and KillProcessTreeInternal is now entirely behind #if NETFRAMEWORK

[Copilot]

Pull request overview

Updates the ProcessWrapper test helper to use the built-in process-tree termination API on modern .NET, while keeping the existing WMI-based recursive kill for .NET Framework.

Changes:

• On non-.NET Framework targets, uses Process.Kill(entireProcessTree: true) directly from KillProcessTree.
• Restricts KillProcessTreeInternal (WMI recursion) to #if NETFRAMEWORK.
• Ensures Process instances are disposed via using.

[adamsitnik]

@copilot address my feedback

[Copilot]

@copilot address my feedback

Both suggestions applied in 060c4a8: bare catch and target-typed new() for ManagementObjectSearcher.

[adamsitnik]

LGTM, @vijayrkn the PR is ready for review