ToolStripTextBox cannot get focus in DemoConsole application

[LeafShi1]

Steps to reproduce

Test sample: DemoConsole in Winforms repo

1. Select ContextMenuStrip control.
2. Add a TextBox/ComboBox/Separator item
3. Select the new item

Current Behavior :
ToolStripTextBox cannot get focus

Expected Behavior：
All items can be focused normally

Notes:
If add a extra ToolStrip control in the Tab page, everything will work well

[Zheng-Li01]

Verified the issue with the main branch of dotnet/winforms repo, the issue have been fixed that all items can be focused normally as below screenshot.