[Dark Mode]Improve visual contrast of the contextMenuStrip1 in dark mode in DemoConsole application

[Zheng-Li01]

.NET version

.NET 9.0.100-rc.2.24453.35

Did it work in .NET Framework?

No

Did it work in any of the earlier releases of .NET Core or .NET 5+?

This is a new feature Dark Mode: #11857

Issue description

Improve visual contrast of the contextMenuStrip1 in dark mode in DemoConsole application.
And the issue also can reproduce on other controls, such as imagelist, timer etc.

Steps to reproduce

1. Clone the DemoConsole in Winforms repo
2. Enable Dark mode by adding below code lines in the Program.cs file under DemoConsole project

#pragma warning disable WFO5001
Application.SetColorMode(SystemColorMode.Dark);

3. Build and run the DemoConsole project
4. Observe the contextMenuStrip1 item

[Olina-Zhang]

Verified in the latest main branch of Winforms repo, it was fixed. But found a regression issue: #13624